will free work? you can find computers in the trash that will run those 100%
ask around for old systems, someone probably has a old system collecting dust, check thrift (junk) stores (although they sometimes over value computer stuff) & get a hold of a copy of fastmame .56 and run it on pretty much any pentium 2 or better system.
probably still run 100% even on newer versions of mame.
you dont need a 2ghz+ system for those.
check ebay or if you can wait check out freecycle.org
they're groups across the country (US), i think even in other countries, you can post stuff to get rid of and others in your area will do the same, old tv's, computers, basically anything other then animals, guns, or porn.
PS. skip the case it's dead weight.
you just need mobo,cpu,ram,hdd, and power supply, just get a scrap piece of board and mount it directly to it using some standoffs, either ruber or plastic washers, or you can make some out of a ball point pen by chopping it up, 3/4 OR 1 inch wood screws should do the trick.