I picked up an ACA1230/42 from amigakit.com and I'm pretty happy with it.
I'd read on the internet that some people had issues.
Certain revisions of the A1200 require a couple of caps or resistors to be removed due to a design flaw in the Amiga. I can't remember the exact details but they gave me a sheet with the instructions on it. It wasn't particularly difficult if you know how to solder.I have a 1D4 revision and I haven't had any problems at all so I haven't bothered to do the mod.
Installation was a bit of a pain. It was easier to open the case and remove the motherboard, and install the accelerator from the top side of the Amiga, than try to install it through the trap door on the underside. You might as well remove the metal shield as well because the accelerator won't fit with it in place - alternatively you could just bend the edge up so it doesn't touch the acclerator. From what I've read there's really not much benefit to leaving it on though.
Also, the floppy they gave me had an outdated version of ACATune that wouldn't detect my accelerator so I had to download a newer version from the web before it would work.
Apart from that though, it works like a charm
The 42MHz model is a bit out of your stated price range but I believe they also make 28MHz versions which are significantly cheaper. They seem pretty thin on the ground at the moment though.
