A few thoughts/experiences...
Reports are that the Q630 will take 128 MB SIMMs. So the capacity would be at least 132 MB. The ones with two slots, again reportedly, cannot use a double-banked SIMM in the second slot, so its limit would be 64 MB for a total of 196 MB. I have not tried this myself.
The video performance on the Q630 is very nice, but I think the VRAM capacity may leave something to be desired.
The edge connector on the motherboard of the Q630 makes it an unlikely candidate for installing in an SE/30, unless you want to adapt all your connections to that edge connector.
The Q63x and related Performas and LCs can be taken to 40 MHz with a simple resistor moving hack. As for all such hacks, see Marc Schrier's Clock Chipping Home page for details.
While it is possible to do SCSI RAID on 68040 machines, I think you'll find the results disappointing and actually slower than getting a single hard drive with performance that can saturate your interface. Kaye (of MacGurus) has done many RAID tests on PPC NuBus hardware with dual JackHammers and very fast SCSI drives and found that the performance was not substantially better than single drives. A single fast drive can so saturate the NuBus, that there is no advantage in running two drives at a time.
Now, if all you have is older slower SCSI drives, then a RAID could add some performance. For example. while the interface on an ST32550N (very early 2 GB Barracuda) is rated for 10 MB/s (Fast SCSI II) the drive itself can only deliver about 6 MB/s of performance. Similarly, the ST32550W (Wide version) is rated for 20 MB/s interface performance, but again, only delivers about 6 MB/s of performance. They have the same disk mechanism, and that's the best the platters and heads can deliver at 7200 RPM.
Combined in a RAID 0 on a single Jackhammer in a Power Computing Power 120 (120 MHz 8100 clone) two ST32550W drives give about 8 MB/s of performance. In other words, nowhere near double what a single drive delivers.
If one adds a third drive to the JackHammer and the RAID, performance does not improve in any measureable way.
However, if one then puts an ST32550N on the built-in Fast SCSI bus, and adds it to the RAID, the performance is boosted to 10 MB/s. Adding a second drive to the FAST SCSI bus does not improve performance. Finally, adding a fourth drive, another ST32550N to the built-in unenhanced (5 MB/s) SCSI bus and adding this fourth drive to the RAID brings total performance to 12 MB/s.
Pretty pathetic (and noisy and hot, the early Barracudas were *NOISY* and *HOT*) performance for the amount of effort input.
It is possible that Quadra results might be different, since the NuBus interface to the host machine is a bit different, but I doubt it.
If one buys a newer SCSI drive, which will also be quieter and cooler running, which delivers performance in the neighborhood of 20 - 30 MB/s and puts it on the JackHammer, one will almost certainly see much better performance than can be achieved with a RAID of older slower drives. And adding more new drives to the RAID won't really improve performance because one fast drive bottlenecks the NuBus.
Reports are that the Q630 will take 128 MB SIMMs. So the capacity would be at least 132 MB. The ones with two slots, again reportedly, cannot use a double-banked SIMM in the second slot, so its limit would be 64 MB for a total of 196 MB. I have not tried this myself.
The video performance on the Q630 is very nice, but I think the VRAM capacity may leave something to be desired.
The edge connector on the motherboard of the Q630 makes it an unlikely candidate for installing in an SE/30, unless you want to adapt all your connections to that edge connector.
The Q63x and related Performas and LCs can be taken to 40 MHz with a simple resistor moving hack. As for all such hacks, see Marc Schrier's Clock Chipping Home page for details.
While it is possible to do SCSI RAID on 68040 machines, I think you'll find the results disappointing and actually slower than getting a single hard drive with performance that can saturate your interface. Kaye (of MacGurus) has done many RAID tests on PPC NuBus hardware with dual JackHammers and very fast SCSI drives and found that the performance was not substantially better than single drives. A single fast drive can so saturate the NuBus, that there is no advantage in running two drives at a time.
Now, if all you have is older slower SCSI drives, then a RAID could add some performance. For example. while the interface on an ST32550N (very early 2 GB Barracuda) is rated for 10 MB/s (Fast SCSI II) the drive itself can only deliver about 6 MB/s of performance. Similarly, the ST32550W (Wide version) is rated for 20 MB/s interface performance, but again, only delivers about 6 MB/s of performance. They have the same disk mechanism, and that's the best the platters and heads can deliver at 7200 RPM.
Combined in a RAID 0 on a single Jackhammer in a Power Computing Power 120 (120 MHz 8100 clone) two ST32550W drives give about 8 MB/s of performance. In other words, nowhere near double what a single drive delivers.
If one adds a third drive to the JackHammer and the RAID, performance does not improve in any measureable way.
However, if one then puts an ST32550N on the built-in Fast SCSI bus, and adds it to the RAID, the performance is boosted to 10 MB/s. Adding a second drive to the FAST SCSI bus does not improve performance. Finally, adding a fourth drive, another ST32550N to the built-in unenhanced (5 MB/s) SCSI bus and adding this fourth drive to the RAID brings total performance to 12 MB/s.
Pretty pathetic (and noisy and hot, the early Barracudas were *NOISY* and *HOT*) performance for the amount of effort input.
It is possible that Quadra results might be different, since the NuBus interface to the host machine is a bit different, but I doubt it.
If one buys a newer SCSI drive, which will also be quieter and cooler running, which delivers performance in the neighborhood of 20 - 30 MB/s and puts it on the JackHammer, one will almost certainly see much better performance than can be achieved with a RAID of older slower drives. And adding more new drives to the RAID won't really improve performance because one fast drive bottlenecks the NuBus.