I currently play an Ibanez RGT42DX through a Line 6 Spider III amp. Of course, I got the Spider III when I was a beginner, and it worked well for my needs then. Well, I've started researching amplifiers and I've played different types of amps and I feel like I want to move on to tubes. I'm not entirely sure what my budget is since this is going to be a combined birthday/Christmas present, but I'm thinking $800 would be the max. Now I know my options will be limited, but if anyone could give me any recommendations on any new tube amps, or give me an idea of what I could get used, it would be appreciated. I play a lot of Foo Fighters, Silversun Pickups, Muse, The Killers, The Police and Protest the Hero. I also experiment a lot with jazz and blues, but rock is really more my focus.

So, now that I got all that out of the way, what can you guys recommend I try out? I've been reading about the Peavey Valveking 112, but I'm seeing a lot of mixed reviews about it. I will of course be trying things out, but it'd be great to get an idea of what to look at.

For that budget the world is your oyster. 800 smacks can get you a lot in the used Tube market, if you can buy used.

Look into a Marshall JCM 900. Good old school sound for the bands you listed, head's can run you anywhere from 500-900, and you'd still need speakers, but you can find a good combo version for less than 600 on occassions, (ebay, CL).

I'd look at a Vox AC15 if I was you, a lot of that "Bright" distortion comes from those Class A sounds. Dont discount a class A tube amp at 15 watts or less, they get a hell of a lot louder than you think.

Find UG's Chuck and ask him about gigging on 1Watt of Tube Power on his Rebel. You'd be in the tone ball park for the Killers with a sound like that.
1981 Gibson Les Paul Custom (Black Beauty)
1980 Marshall JMP 2204
I think you could find a decent JCM 900 or DSL 401 used on Ebay, Craigslist, or Guitar Center. That would definitely be a great choice. I would also look at Bugera and the Egnater Renegade series (smaller tubes but still nice). You can get some great sounds from the vox amp modeling but I rather have a good tube + choice of pedals.

My Gear:
Guitars: Vintage LP, Martin DX-1, Epi Viola Bass,
Amps: Marshall JMD501
Effects: Empty Set right now