Thanks for the replies guys! :-)
The exact version of the 2.05 ROM that WinUAE requires for A600 emulation is 37.350. The exact version of my A500+ 2.04 ROM is 37.175. Looks like I may have to get an A600 just for the ROM, although I may just settle for A500+ emulation, where the only difference is the ROM version (both have ECS, 1MB RAM etc). :-)
Steve.