What's a good brand to go w/ that's not too pricey?  I can still get the cheap deal on mags from SA for buying the gun, but I'm not sure that I want to, especially if there's something better out there.  

Truthfully, all the ones I ever tried in my SA worked without fail.
I suppose the key here would be long term use.
I have never had to change springs in any yet either, for that matter.
IMO, it's nice to have a variety, a few of each type, most here would say Wilson or CMC power mags.
Some seem content with the military contract 7 rounders.
Conversely, some don't like the SA factory mags, for whatever reason.
If your SA specimen has been reliable, you may not have to goof around to find one it likes.

For quality, I like Wilson mags, but they are spendy. For range mags, try here: www.aspitactical.com/genuinegi/details/ver8-21001.asp?PRODUCT_ID=21001.

Apparently they are currently on back order, as I have been waiting for a while for mine. Although, it is always nice to patronize a site sponsor.

I buy 8rd Chip McCormick mags for about $15 each. They've worked perfect for me.

Shooting Star 8 rounders are a good "inexpensive" mag.  But overall best are Wilson's in my book.  Pricey, but they never fail.

www.precisionsights.com/actmag.html

Truely beautiful mags...and cheap.

For the best, by reputation (I haven't tried any, but seen many used), get Wilson mags.  Good for competition and self defense.  They will be functional and reliable.  

Second to the Wilson mags would be the Chip McCormick Power Mags.  

Then would be the CmC Shooting Star.  Good for range use.  I've used half a dozen of these, and never had a failure.  The springs feel quite light, tho, so they will be relegated to range only use.  

Wolff has a 7 round mag that's supposed to be nice.  I hope they do an 8 rounder.  

Below these, I'd go with USGI.  ProMag isn't bad... USA is crap.  Triple K is junk.

Chip McCormick 8-rnd Shooting Star mags offer the best balance of price & features. They have been flawless performers for me.

Quoted: Conversely, some don't like the SA factory mags, for whatever reason.

Becasue it only holds seven rounds and has sharp feed lips that abrade my thumb, as opposed to the smooth feedlips of a Wilson, Metalform, MecGar, or Chip McCormick mag.

For range mags, go to the next funshow and look around for USGI mags.  At one of the local shows, I'm able to get new-in-wrap GI mags for $8 each.  Just beware of the ones with the witness holes in the wrong place... I got one that's a little too wide and binds in the magwell.  Aside from that one, the other 7 that I have (that aren't mis-drilled) are flawless.

A step up from that, my McCormick mags haven't choked yet.

EDIT:  The ones at ASPI tactical are the ones with the witness holes in the wrong place, as you can see from the pic.  You see noted that the manufacturer code listed is 30745.  Ammoman also had some of these mags a while back.

Mine are all mfr. code 1M291, which seem to be plentiful and cheap in my neck of the woods, and are 100% reliable and in-spec.

CDNN

Another vote for the Chip McCormick Shotting Star mag.  

What's the difference b/t the 7 & 8 round mags?  Do the 8's stick out a little, or do they simply just hold an extra round?

Quoted:
What's the difference b/t the 7 & 8 round mags?  Do the 8's stick out a little, or do they simply just hold an extra round?[/quote
A redesigned follower allows that extra round to fit.
It does not hang down but the added plastic floorplate does on both, the 7 & 8 rounders.