If you do this I'd pay for one. I'd have to pick up another A500 but I'd pay for one. I think, despite what the classic gamers here say, that more RAM is crucial. Also IDE and of course CPU (whole point) is equally crucial. I would definitely pay more for a board that included a cheap RTG solution. The primary reason is that the A500 has no easy way to output better graphics. No video slot and the graffiti is not worth it for an A500 due to the ECS chipset limitations.
In order (bare minimums are):
040/060 (jumper switchable)
32MB minimum RAM
IDE capability.
Things I would definitely pay more for
RTG Graphics (IMHO this is very important for A500/A600)
Built in Ethernet
Coldfire/PPC (possibly with socketable 040/060)
128+MB of RAM
IDE capability
PCI expansion header
Many people seem to want an A500 for classic gaming. I can see the point but honestly if thats all you want it for, pick up an A500 with a 512K ram expansion and leave it be. Almost all classic games with run with this.
If you're going to buy an accelerator you don't want to get close but never be able to truly enjoy 3.9 or any modern software update (perhaps better browsers and such) due to lack of RTG when RTG could have been on the drawing board. Developers who'd like an extra miggy for dev purposes would be sad to have to run a compiler with 32MB of RAM.
If you're going to solder RAM, put more RAM on there. Even at 128 the prices are so cheap theres no reason not to. If you have a socket then leave it bare and let the user install it. Then the people wanting 4MB can use 4MB and be happy.
I think IDE is very important for obvious reasons. And finally ethernet is important for the same reasons that RTG are. There is very little to no expansion capability for this type of upgrade on the Amiga 500. The Amiga 600 at least has a PCMCIA slot to account and allow for this but if I am not mistaken this slot is almost always used for some other expansion (such as RAM, HDD, etc...)
