If the gentleman already has a 1200, going out and shelling out 400+ dollars for a 4000 is probably not the way to go.
Get one of the ACA cards if they are still available. For most classic amiga stuff, an 030 will do great, and they have more RAM than you'll know what to do with.
Graphics cards are nice but I guess I never felt the need. Seems to make it more of a PC. I got one of those already.