To be honest, 9.1 is too much for an old Mac like that. The maximum RAM that machine can handle is about 64 MB, and at 75 MHz along with a slow hard drive the experience you're going to have is an unpleasantly slow one.
With those Macs, the best Mac OS to run on them would be 7.6.1. Lots of older apps still support 7.6.1 such as the iCab web browser. You could go for 8.1, but the newer interface and extra features might slow it down as well.
When I used to live with my parents, I used to have a Power Macintosh Performa 6220CD which was basically the same thing as the PM 6200 except that mine had a TV tuner card built-in. It had a 75 MHz PPC603 processor and I maxxed it out to 64 MB of RAM. It was snappy under System 7.5.5, but was noticably slower under 8.1 though still usable. After installing 9.1 on it, startups were super slow as well as general OS tasks. So I would recommend 7.6.1, which is what I'll probably install on that 6220CD that my parents still have at their house.
While you could upgrade the hard drive, remember that the controller is old and might not support faster speeds or storage capacities. More information can be found at this link from Low End Mac:
http://lowendmac.com/ppc/6200.shtml
With those Macs, the best Mac OS to run on them would be 7.6.1. Lots of older apps still support 7.6.1 such as the iCab web browser. You could go for 8.1, but the newer interface and extra features might slow it down as well.
When I used to live with my parents, I used to have a Power Macintosh Performa 6220CD which was basically the same thing as the PM 6200 except that mine had a TV tuner card built-in. It had a 75 MHz PPC603 processor and I maxxed it out to 64 MB of RAM. It was snappy under System 7.5.5, but was noticably slower under 8.1 though still usable. After installing 9.1 on it, startups were super slow as well as general OS tasks. So I would recommend 7.6.1, which is what I'll probably install on that 6220CD that my parents still have at their house.
While you could upgrade the hard drive, remember that the controller is old and might not support faster speeds or storage capacities. More information can be found at this link from Low End Mac:
http://lowendmac.com/ppc/6200.shtml