Also a note on the STV, its the same boat as the naomi is, most of the STV games were rleeased on saturn, and well, are the same games. Since the STV is just a saturn, like naomi is just a DC.
However there are a few cool STV games that were not released on saturn, and STV is standard jamma, you could compare STV to MVS, it uses the cart system, and the carts are almost the same size as MVS ones.
I have owned a CPS2 unit many times, the easiest thing to do is Get an A board, and when you buy a game, play it foy 6 monthes, a year whatever, sell it off and get another one ect.
Since the CPS2 games do die, its better not to "Collect" them in the old fashioned sense, get them, play the hell out of them, and when your done sell them. Always keep your A board though (The A board doesnt suffer from suicide).
CPS3 is the same deal, the CPS3 board itself has no suicide in it, but it uses a CD, cart combo. The entire CPS3 game is loaded from CD into the boards ram, the security cart for the game must be in the board for the game to work. Since its a CD based system, you can easily copy the game, however it wont run without the security cart.
Inside the cart is a suicide battery just like CPS2, so once the cart dies, your whole board is useless, unless you can find another security cart (Which wont be easy to find).
Ive had a Warzard Cart die on me before and was screwed.
Just dont try to collect and keep CPS2 or 3 stuff and youll be fine. I dont know of any other boards that use suicide batterys, Taito F3, STV, MVS are all good systems to get.