How much ya lookin to spend? There is cheap, and there is elaborate. Just a matter of doing it properly no matter the budget. I have way too many recommendations and combinations for PC based builds that it isn't funny. Personally, I prefer PC over Pi. As for requirements.. yeah, don't sweat it or worry about it. Just to be funny, here is an arcade cabinet I built a few months back that runs on an old Pentium 4 with Windows XP.
So pretty much,... in a nut shell.... if it will PC, it will arcade. If it arcade's, then it can run emulators. Before going any further, again, I ask.. so how much you looking to spend? You have something now you are looking to convert? Want to try your hand at new?
Welcome to the hobby.