1st Amp head what should I buy $500 +/-

You can't go wrong with one of those Aguilar amps for your first, and even, your forever amp.

 

I was considering a TH 500 a while back. I ended up getting an Ampeg PF 500 head. The growing pains of this amp were ironed out a while back and it has been totally reliable. It's a bit bigger in size than the TH but that was no big deal for me. Fits in a Targus laptop bag nicely and has a zip pocket for connecting wires and some other stuff. If I recall correctly , the PF was about half the cost of the TH. I gig regularly with this amp.
If you plan on getting into a band situation in the future , a single 10 or 12 will probably not be enough. Save up for a couple of 2 10 cabs or a good 2 12 cab. These will usually get you through most band situations. I'm currently using a 2 12 av cab from Ampeg and it is more than enough to get me through both of the bands I have played with it. Before that , I was using an 8 10 cab. It was also more than enough by a long shot. My current band is fairly loud with a mic'd horn section and mic'd drums. I don't need to go through the PA with the 2 12.
You will probably get a bunch of different ideas from others in here and I am sure they would work well too. I'm just telling you what has worked well for me. Rock on.

 

So long as you speaker cabinet can handle to potential power, the 500 is not all that more expensive than the 350, in the long run. The two speaker outs are just added convenience as most speaker cabinets should have two connectors for daisy-chaining more cabinets. If you don't plan on more than just the one cabinet you have in mind, it's irrelevant, anyway.

 

Pick up one of the used Quilter BB800s and put the rest toward a good cab. I’ve been through a ton of high end gear, and the BB800 is a wonderful head at a steal of a price.

 

Ampeg PF500/800

 

+1 on this. I've been through a lot of heads and the Quilter BB800 is among the best at any price.

 

I assume you don't have the cabinet yet? You might want to think in terms of total budget for head+cab. This is especially helpful because you might want to consider used gear which often comes as a set, for a nice price. Why used? You'll get more bang for your buck, and since you're just starting out, you'll likely get the itch to try something different at some point in the future. You're just starting to learn what you like and need. When the time comes to sell this set of gear, you can get most of your money back if you buy it used to begin with.

 

You'll get a bunch of answers. I've always purchased my gear second hand and have never had a problem buying from sellers who value their reputation whether here, on eBay or Reverb. That said, I recently picked up an early Markbass LMIII that I've been pleased with as a backup. You'll have funds to spare and it's tiny/light weight. You'll read opinions here from others that don't like this amp, particularly in it's most recently produced model. If I were to consider a 3rd brand (Mesa is my "A" rig), I'd take a look at G-K.

Enjoy the hunt but try as many as you can.

 

Making your decision based on a TalkBass popularity contest is not a good idea. Research the amps mentioned here and read other reviews. Also see if there is any commonality in the amps your favorite bass players are using. Also keep in mind that amps react differently to different cabs. Just because an amp may sound good with one cab does not mean it will sound good with yours. I suggest buying new from a dealer that has a good return policy like Musicians Friend so you can try them out.

And after I've said all of that here's another to consider. It's $100 off now with preorder and will go up when they start shipping in 2 weeks. The Fender Rumble is a very popular amp with a 2 year warranty.

https://www.musiciansfriend.com/amplifiers-effects/fender-rumble-800-800w-bass-amp-head?rNtt=fender rumble&index=11

And if you want to save some money on the Rumble head that was just discontinued last month go here:

Brand New "Fender Rumble 500 Bass Amp Head"

 

If you can, try before buying. I've heard good things about Aguilar and I believe the are made in N.Y. Go 500 min.

 

In addition to sounding different with different cabs, you need to think about what kind of music you'll be playing...Amps (and cabs) coupled with your bass and your playing technique will greatly effect the tone and ability to find your musical "voice". As a new player, these factors will most likely go through an evolution over time. It's a good bet that this first amp won't be your forever amp.

That said, it's solid advice to see if you can find a way to do a live test. So many good choices of equipment out there and so many good sellers here, I don't envy you. Good luck.