Good budget tube amp?

as far as compatibility with my speakers goes, is it just the impedance I need to worry about? So, whether it can handle 4ohm/8ohm, etc? Also, in my searches, are there any amps that I should definitely stay away from?

Well, you have some pretty good suggestions above if you can find 'em; let's see what an "alternative" picture might look like. If you are buying new and are committed to retaining the Rainmakers, then have a look at Bob Latino's Dynaco-derived KT-120(easy)kit for KT-88's, et.al. Bob's eBay spots had a more useful one-shot presentation on this amp than the main website, the last time I looked. Documentation is said to be thorough for first-time builders, and options are set out clearly. Bob seems to have favored the Gold Lion Reissue KT-88's in this design for awhile, but there are other choices, both cheaper (some say the E-H KT-88's are fine), and dearer (Shuguang Treasure Series, et.al.). I'd opt for appropriate NOS tubes at the input, if not right away, then when you can: Bob, or someone like Jim McShane can surely guide you here (G**gle).

Some practical benefits of this choice: Work slowly, wire it with consistent, symmetrical, and "artistic" neatness; make the practical/premium choices in the "non-consumables" and input tubes; take photos as you go and record all the reasons YOUR build is "as good as you'll ever see"... and the inherent value, your retained value (for if and when you upgrade), will probably exceed comfortably your other options buying new. Your true cost -- that is, the real "price" -- is your total cost of ownership. Therefore, this might be your most economical choice, as well as potentially the best sounding. Of course, who can say what might show up in the listings here worth grabbing with little hesitation!

My personal choice might be for "[slowly] appreciating assets" among the vintage amp listings on eBay, and sometimes here: recognized "classics" like Pilot SA-232 and SA-260 (if bidding doesn't get overheated), and other broadly-respected units such as Eico HF-87 and Fisher SA-100. Also consider well-accepted models the whole crowd hasn't gotten hip to (i.e., bargains): various 7189/EL-84/6BQ5 Heathkits -- AA-151 is a good, low-cost choice (with some modding)-- Fisher SA-16, Stromberg-Carlson ASR 333/433, Sherwood S-5000 II and S-5500 --> version IV 7868 amps (stylish, if they're to your taste -- my late S-5500 IV is less rats-nest-y under the hood than earlier iterations, which = easier to work on); as well as the option of two decent integrateds to use as "monoblocks" (I picked up -- "submitted for your approval", as Rod Serling used to say -- in separate transactions, two VERY clean Heathkit AA-181's, ~23 watts/ch., with original tubes -- 7591's + the small tubes, worth approximately the cost of the amps themselves! -- for WELL under three hundred bucks). Figure $200 for refurb by a qualified person, maybe less, maybe a bit more... and you're there, depending on what sensible, straightforward mods may be advisable. Many know what to do here. In cases involving the integrateds especially, you'll probably want some wiring and control circuits up front bypassed, which is not a big deal; but read the vintage and DIY forums for guidance and caveats. You can also get an idea who can perform the work -- all of it, or some -- as you go along. Just G**gle.

For the latter choices, you'd want more sensitive and/or tube-friendly speakers, so it would be kind of a sea change for you. You didn't mention musical tastes, and that will have much to do with deciding which speakers would be suitable for the power on tap. I'm setting up a vintage-y system now myself (partly as a hedge against the economic effects of any more dubious four trillion dollar wars... or similar little faux pas -- seriously... I'm semi-retired and vulnerable). Through Audiogon, I have Silverline SR-15's & Minuets, plus Jordan wide-rangers to experiment with. There are the usual high sensitivity options (Tekton Lore [?], e.g.); also check out models that, at first glance, seem too "insensitive", because a few of these can surprise, if you have a small room or rarely CRANK it. Two examples I've seen vouched for in this regard -- though I cannot do so directly -- are the last iteration ACI Sapphires before the smaller Emeralds (by the designer); and the PSB Synchrony 1B's, if Andrew Marshall and 'Audio Ideas Guide' can be believed here (2A3's?!).

In sum, that's one sort of survey of the not too "specialized" tube universe from circa $1000, on "down". Have fun!

I share your opinion when it comes to Rogue Audio amplifiers and currently own a Stereo 90.I also own and love a Raysonic SP-120 KT-88 based integrated.It is great sounding,very dynamic,and the quietest tube amp I have owned.You may be able to find a NOS SP-120 or its EL-34 based SP-100 sibling at or near your price point.They have been replaced with mk.II versions.The differences (between the original and Mk.II) are mainly cosmetic.
Though a notch down from the Raysonic,the affordable Yarland amps do a decent job as well

There are a lot of good suggestions here.

However, I would encourage you to check out a true blue Dynaco ST70, either used, or new and available through Kevin at http://www.dynakitparts.com If you need someone to build it for you, he has a network of folks to provide that.

For all the criticism leveled at the ST70 over the past half centure, it remains one of the touchstone products in audio, and possesses a magic that most high-end audio components never come close to. The only real negatives I find with it are 1) lack of power compared to a larger amp and 2) subpar performance in the low frequencies. It took me 25 years of overlooking them, only to discover as one of the finest, most engaging products I've encountered.

Trelja makes a fair point regarding the ST-70. Note that Mr. Latino can also supply an all new, "modernized" version of this that addresses these issues to a useful degree, and the Dynaco pedigree look is retained. Keep in mind that no matter how many raves you hear about this or that amplifier from the so-called "Golden Age", practically all of these were designed under serious cost constraints for a MASS MARKET. There was neither much of a "high end" as we know it today, nor a hardcore consumer subculture for extremely pricey solutions or boutique parts, status symbols not withstanding.

I think you'll find the KT-88/6550 version I mentioned with the beefier transformers more economical in the long run: the "supply side" constraint on resale prices and "appreciation" of the standard ST-70 and its many variants is pretty obvious. Then, too, your options for speaker choices (and speaker bargains!) are expanded. You can always use EL-34's or 6CA7's in the he-man version, if that better suits your taste in sonics. Also consider that triode mode switching and an input attenuator with gain/sensitivity options via tube choice are available, too. Work through the math, consider the market's alternatives... you'll see.