ROM 03 IIgs are gold, it's the machine that everybody wants because it can run GSOS (Apple II version of the Mac Graphic System). There are other things it can do that the other two IIgs' can't. I think you can upgrade it to 8Megs while the ROM 0/1/2 can only go up to 2Megs, even if the card supported more RAM, the computer did not.
Back to the Apple IIe; some people would buy a 65C02 and put them into the IIe because it was cheaper but they did not have the ROMs to make it an official //e. In 1982 you could get a 65C02 for $35 ($20 by 1984), while the Apple Upgrade was $199. A 6502 went for $12 - $20 depending on which one it was (MOS, Synertek, Rockwell, Western Digital, etc.) I used to put 65C02s into my Commodores (Vic 20, 1540/1541 Drives, PET so on) and Ataris (800s and 400s), and they ran faster and in the case of the 1540 & 1541 disk drives, ran cooler.
Back to the Apple IIe; some people would buy a 65C02 and put them into the IIe because it was cheaper but they did not have the ROMs to make it an official //e. In 1982 you could get a 65C02 for $35 ($20 by 1984), while the Apple Upgrade was $199. A 6502 went for $12 - $20 depending on which one it was (MOS, Synertek, Rockwell, Western Digital, etc.) I used to put 65C02s into my Commodores (Vic 20, 1540/1541 Drives, PET so on) and Ataris (800s and 400s), and they ran faster and in the case of the 1540 & 1541 disk drives, ran cooler.