I have to agree with others who've said that your speaker choice is a bit odd for an HT system. Can't argue with individual preference, though. Since you like them, and want to power them cheaply, I'll offer a few suggestions.
A good tube amp, unless you can pick one up at a yard or estate sale, will be hard to find within your price range. Older solid state amps, reasonably priced, can be found on eBay. A search using "Onkyo m" or "Sony TA" as your keywords will reveal quite a few. The Onkyo M-501, for instance, can often be found under $100. A pair of them would suit your needs nicely. A single M-504 would also work (it looks cool, too). Some fine old Sony power amps, like the TA-N55es, can be had for about $400. Other good Sony es models are much cheaper.
If you want a simpler set-up utilizing a used integrated amp, the Sony es line ( older 5.1 units) still offer fine performance at a good price. The new integrated digital Sony amps have what some consider a "tube like" sound. A used or refurbished DA-3000es 7.1 (150 watts per channel) sells in the $400 range.
Other brands offer some fine choices, too, but since they are usually more prized by vintage equipment fans, prices are generally higher.
