Ken, all competently designed modern receivers are "4 ohm compatible-ish". As always, the question is how loud and how long they're played, but except at extremely loud and prolonged levels relatively easy to drive speakers such as Axiom M80s should cause no problem.
The 2112 is rated at 90 watts and the 609 at 100 watts, and there's a trivial difference of less than 1dB in maximum sound level between them or one rated at say 110 watts. Either should be okay power-wise, but for overall features within your budget you should instead be looking at the 709 rather than the 609. It has the significant advantage of Audyssey MultEQ XT rather than 2EQ. Besides more measurement positions and higher resolution filters, the all important difference is that it equalizes the sub channel, which usually needs it most, while 2EQ doesn't(odd that Onkyo continues to put it on a model two steps up from base).
Yes, you should be looking right now, among other reasons being that ShopOnkyo's Christmas sale with an additional 25% off certain refurbs runs until December 29. Here's
the page, and that refurb price is reduced 25% for "Club Onkyo" members the next couple days. Registering for the Club you get a $10 purchase credit, so the overall shipped price would be about $477. There's also a 5% credit given which could be used on a future purchase. Taking shipping into account, this is about $35 better than the current A4L deal.