Here's the deal. If you are only going to use one cab, go with the lower ohmage cab as long as your amp can handle it. It will be louder that way. If you ever plan on going with two it gets more complicated because, depending on how you wire it, the total ohmage the amp sees is lower than either cabs ohmage. But for one cab set ups, I would just get the 4 ohm and make sure your amp can handle it. I've also heard nothing but good things from Avatar, although I heard their lows weren't as bomb as something high end like a Bergantino or some other such expensive thing. However, with a limited budget you can't be that much of a chooser, and like everyone else said, the Avatars aren't bad, they may just not be what some people wanted tone wise. As far as amps, I would recommend a pre-power setup (preamp and poweramp). About a year ago I was in the exact same boat you are, and I ended up going with a used BBE preamp (that's just a brand name) and one of the cheaper QSC(brand) poweramps. I got the pre on our very own talkbass for 150 I think. The amp was I think either 3 or 4 hundred on one of the big evil empire online stores. The tone is to die for and I have something like 1000 watts when I run it into one cab. The pluses of my setup are that it ended up costing what most heads with 3 to 4 hundred watts would cost, and since these setups are more modular, if I wanted to change my power output or my tone, I don't have to go for a whole new rig, I can just replace one piece. I love it. My cab is an SWR Triad, which I fell in love with in the used section of my Guitar Center (again with the evil empires), but I got it for about 4 or 5 hundred, and I can't see ever changing it since it sounds so awesome. Now, this is all me, and my tastes, so take this with a grain of salt. And transporting a rig is much harder than transporting a combo. Which reminds me, there are some combos for about the same price as a cheap rig with several hundred watts that might fit your bill. I checked some of those out before I bought my stuff. I think Eden and Fender (only two I tried) have 2x10 combos with several hundred watts that would be about the same price and much easier to transport. The problem with them is if you want to change anything, you have to buy a whole new everything. Being an engineer, I liked the more modular rack setup. Anyway, I'm done.