If you are to use an internal Mini-ITX/Flex-ATX type PSU you shouldn't have a problem getting a PSU which has the potential to supply 200+ W with very high efficiency even at a low load (say if in reality the board really only requires/consumes not more than 60W).
About PSU's: PSU's are not 100% efficient when converting from AC to DC, some power will be lost in the conversion process - generally has heat. Also, depending on the actual load on a PSU, the percentage of efficency in conversion varies. For example, a 100W power supply may convert at about 85% efficiencty at full load, meaning that the actual DC output is aproximately 85W at full load. The same supply only converts at about 45% effiency at a low load level, hence if you hook up a device which doesn't require much power, you may end up only having 45W available rather than the rated 100W. Therefore, a bigger PSU may not necessarily be the better solution, something in closer proximity to the minimum/maximum load would be more ideal. Generally, look for the "80 Plus" rating when shopping for PSU's. This rating guarantees that the PSU will be capable of running at 80% efficiency (at least) on all load levels.
I am actually using a 220W PSU (FSP220-60LE 80 Plus) to drive my 6500 board in a Colour Classic, since the stock supply doesn't supply quite enough juice. I'm quite sure that the external 65W PSU will not supply enough power to properly run the board, especially if you want to use a G3 upgrade card. If you were to get an external PSU capable of outputting at least 100W - 120W I would assume that you should be okay. I would consider using low-power addon options if you're not sure whether the PSU will be able to supply enough juice (for example, using a IDE-Compact Flash solution rather than a fullsized 3.5" hard drive). Get something very efficient and over 100W and I think you'd be alright.
-- BeniD82
About PSU's: PSU's are not 100% efficient when converting from AC to DC, some power will be lost in the conversion process - generally has heat. Also, depending on the actual load on a PSU, the percentage of efficency in conversion varies. For example, a 100W power supply may convert at about 85% efficiencty at full load, meaning that the actual DC output is aproximately 85W at full load. The same supply only converts at about 45% effiency at a low load level, hence if you hook up a device which doesn't require much power, you may end up only having 45W available rather than the rated 100W. Therefore, a bigger PSU may not necessarily be the better solution, something in closer proximity to the minimum/maximum load would be more ideal. Generally, look for the "80 Plus" rating when shopping for PSU's. This rating guarantees that the PSU will be capable of running at 80% efficiency (at least) on all load levels.
I am actually using a 220W PSU (FSP220-60LE 80 Plus) to drive my 6500 board in a Colour Classic, since the stock supply doesn't supply quite enough juice. I'm quite sure that the external 65W PSU will not supply enough power to properly run the board, especially if you want to use a G3 upgrade card. If you were to get an external PSU capable of outputting at least 100W - 120W I would assume that you should be okay. I would consider using low-power addon options if you're not sure whether the PSU will be able to supply enough juice (for example, using a IDE-Compact Flash solution rather than a fullsized 3.5" hard drive). Get something very efficient and over 100W and I think you'd be alright.
-- BeniD82