Looking for suggestions for a decent amp for band practice and/or gigging for $300 or less. Nearly anything would be an upgrade compared to the Crate I've been using, but I want to make sure I get the best bang for my buck. I generally play hard rock/metal and alternative type stuff. So far I've been considering these:

Peavey Bandit
Marshall CFX or DFX
Fender Mustang

(I've seen a few tube amps that weren't too expensive, but I'm somewhat worried about cost of upkeep. How often do tubes generally need to be replaced?)

Any suggestions or input would be greatly appreciated

used Peavey Valveking. also look at the Peavey VIP /Vypyr series of amps. you'd need the highest wattage of those to play in a band. if you can find the tube - hybrid version that would be the best. 
I've heard many good things about the valveking and vypyr. Would you say one is superior over the other? I've been somewhat hesitant about getting a tube amp because I know so little about them (price/upkeep), but i'm leaning more and more towards them the more I hear.
well i prefer the Valveking  but the VIP/Vyper series is also good. the VK is a tube amp and can be has used within your price range. you'd need to get an overdrive pedal for metal . as for upkeep well you'll need tubes every few years (depending on how much you use the amp.) not really all that much to worry about outside of common sense. 
I second the valve king. I have a vk212 with a pair of Texas heat speakers and it sounds pretty good for being a budget tube amp.
If you can find a used Peavey XXX Super 40 that will give you all the power you'll ever need.  You can usually find them used under $300.  I picked one up for fun and it quickly became one of two of my main amps.

Tube maintenance really isn't as bad as some make it out to be.  I change out the power tubes every couple of years and the preamp tubes every 5.  Unless you get a bad one, they usually last at least that long, and can last MUCH longer if you need them to. 
Peavey Ultra 112
Charvel So-Cal (SH6TB/N, killswitch), Jackson RR5FR (TB6/Jazz, Drop C). Joyo pxl pro.
Loop1=Crybaby from hell, Boss PS-5, Seymour Duncan 805 or Green Rhino, EQD Hoof or Earthbound Audio Super Collider. Loop 1 into ISP Decimator II.
Loop 2 (FX loop)-Line6 M9, TC Spark Mini. Loop 2 into mxr 10band. All into a Peavey Triple XXX 212, Ibanez IL15.
I'd also chime in and say that tubes are not as bad as people make them out to be. Most of amps are tube, and my current live rig had its last retube around 2010-2011, still going strong. The rest of the amps have required minimum maintenance. One of my tube preamps started sounding dull, so getting new tubes fixed that. I had a Windsor that kept blowing fuses, that was fixed under warranty but for $300 100 watt amp I can't really complain as it has worked fine afterwards. None of my other amps have had any serious issues.

The most grief I've had has been with solid state amps. My Marshall VS8100 head has seen the repairman twice and my Peavey bass amp 3 times. These were all gigging amps so I'd have to say that even on the road tube amps have behaved better.
Nice, I've been eyeing a valveking at a great price. I'll probably just go ahead and pick it up, assuming noone else has already. Thanks for the help everybody