PC Engine collecting is no more expensive than anyother really.
Import duo-rx or just a duo-r (yahoo.jp for cheap ones! or Risingstuff.com!!!), play every Japanese game (get an arcade card for the measly library if you really gotta) and every CD game ever. most Japanese games worth playing are sooooooooooooooooooooooo cheap. Do a bulk order of like 30 games all at once, you're set for awhile.....
keep your US Turbo Grafx-16, play every US game.
rejoice.
i dunno about around you OP, but theres a shop by me that carries used TG games reasonably cheap like
10$ range cheap!
Most of what was mentioned is also pretty common if you know where to look
There is NO point in wasting the money on a US CD unit. For the price you end up paying you could get a duo-r or rx, which is a better machine altogether.