I need to buy a second amplifier. I've been using the same Super Reverb for years and haven't kept up with what's available. I need a combo with 40 - 50 watts in the $500-$600 range. Does anyone have any ideas or a favorite amp that they would recommend?

I've always been partial to the peavey classic 50 4x10's. They're a nice, solid, and inexpensive tube amp.

You've already got the holy grail of amplifiers. (IMHO) Admittedly, it doesn't do the metal thing without pedal help, but vintage Super Reverbs are in high demand. Is it a blackface or silver face ? What kind of speakers does it have ? I just had my 1974 silver face retubed, recapped, and blackfaced and that baby has never sounded so good. I took it to my regular rehearsal studio and it just blew me and my bandmates away. Just me, my Rick, a cable and the amp. And this place has them all: Mesa, Marshall, Peavey, Soldano, Crate, Roland, Fender TRRI (reissue Twin). I've tried them all. I'm seriously considering lugging my Super to rehearsals from now on (you know what I mean when I say that sucker is heavy). Check out the Fender Forum - http://www.fenderforum.com - for some ideas on tweaking your super. If you want another amp, get another Super Reverb !!!

If I could find another Super in my price range, that would be my first choice. Mine is a '65 model (date code August 65) that I bought from a relative in the Spring of '66. The Super has all original Fender Special Design speakers and has been worked on twice in 35 years - the first time was to replace the line cord with a 3-wire cord, the second was due to my own carelessness, I changed output tubes and didn't have the amp rebiased; some resistors in the output stage failed. This didn't happen overnight, but over a period of years.
I play in a church band (two guitars, keyboard and drums; still looking for a bass player) that plays contemporary Christian music. Pretty cool church! On Wednesdays the band plays for a teen youth service in the basement. I have been lugging the Super up and down a narrow set of stairs for about six months and really need something reasonable that I can leave set up in the basement. I usually play my American Deluxe Strat, but sometimes use my '68 Les Paul Custom (bought new) for a little fuller, heavier sound in the youth service. I use a reissue Tube Screamer and a Dano Chorus and Delay. I have also installed a Hicks Mender, which turns the amp into a channel-switching system, chaining the clean and reverb channel. If I didn't have to keep the volume down, I wouldn't even use the pedals.
I have never felt the urge to replace my Super, so I haven't looked at amps until the upstairs-downstairs trek began. I was hoping to get some opinions about used amps or some of the mid-line tube amps or modeling amps - it's very hard to make a decision based on Music Store trials.

Have you thought about a Deluxe Reverb ? Probably can find one in youe price range. One 12" speaker, 40 lbs (my Super weighs 86 lbs. !), 22 LOUD watts (22 watts is 78% as loud as 50 watts), that incomparable vintage Fender tube tone. If you're not driving the power tubes of your Super (too loud, I know), you can definitely drive a Deluxe and put away some of those pedals. By the way, I strongly recommend you have the all the caps replaced (if you haven't already) in your Super. Aging capacitors slowly suck tone from your amp over time. Your Super is 35 years old and the caps should have been replaced at least twice if not 3 times by now. Just good amplifier maintenance. Also have the pots cleaned, the tube sockets cleaned and retensioned, and have the tech check all your tubes as well. Your blackface Super is selling for $1700 and up ! Fender has just announced a reissue of the '65 Super Reverb - list price I believe was $1799. Take good care of that baby and if you EVER think of selling it let me know ! Good luck.

Ahhh....
I can definately relate to the weight/ bulk issue... my cab is a 2x15- very big, (great for scaring people as I set up), but miserable to move around and generally too big for the places I play so far. Now, I'm not about to get rid of it, I love that cabinet way too much, but I deffinately need an alternate for practicialitie's sake.
Anyone have a 1x15 bass cab kicking around by the way?

The Crate GFX-212+ is 120 watts, had a good distortion, and only costs $419 from http://www.musiciansfriend.com . I can't think of any (new) all-tube amps with that power in that price range. You might consider a 2x12 modeling amp for that price too, just be sure to try before you buy, because some of them sound like crap.

One more vote for the Peavey 30 or 50's!!
I would also check out the Carvin Bel Air models too.

I use the Carvin Belair and like it . I needed an amp for around the house and kept putting it off till my son came home with a 2x12 Behringer . NOT tube but , I like it for low volume stuff at the kitchen table . It's 60 watts .