I have the uniden 520. I like it a lot.
It seems to work as well as my big uniden bearcat (legally tuned) worked but it is smaller. I did add an external speaker which helped out a TON.
I run it with a cheap 4' whip antenna that I think I paid 20 bucks for? The antenna works as well if not better than the several firesticks I have had. I mounted it where the stock radio antenna was and used a splitter so I could share it with the FM/AM radio which I rarely use. The reception on the AM/FM radio suffered after installing the splitter, but the CB still works really well. You can find the 510's and 520's already "peaked and tuned" pretty cheaply.
If space is an issue the cobra 75 works well, it just has a bigger mic since it is all built in. The performance at least on the listening end of the cobra 75's seems to be great after listening to several folks in the club with them use them.