Get the 68060 if you can, but a 68040 is still better than a 68030.
A 25MHz 68040 is fater than a 50MHz 68030 per the benchmarks I used to run, somewhere around 10 to 20% faster. I used to have the 68030 in my A1200 and the 68040 (A3640) in my A3000. I ended up finding a WarpEngine 040/40, no luck at that time with a used 060 board. The 68040 @ 40MHz would open modern JPEG files (somewhere around 1024 x 768) in about 15 to 20 seconds. Eventually I got a "new" GVP 68060 @ 50MHz from SoftHut, the same JPEG files now open in two or three seconds.
