Too funny. I think I have an SX-434 (or a successor) in my semi-functional/broken pile. I'll have to check.
Boy, an SX-1280 is a lot of receiver for a garage. Did you have to sell a car to make room for it?
Speakers? You want speaker?
(warning: course language)
The 1280 will handle pretty much any 8ohm speaker so it's up to you and how you'll use them. Block party or background music?
For the garage my preference is for something sort of mechanical and physically rugged like a "metal brick" style speaker. The classic, old school, commonly available ebay/garage sale/thrift store brick would be the Realistic (Radio Shack) Minimus 7. As long as you don't need deep bass and don't try to play them too loud they should work fine. Your 1280 could probably blow them apart if you try but as long as you don't get all head-bangy they'd be OK.
I already have some cheap Audiosource bricks set aside for the garage (whenever I get around to clearing a space for a receiver) but If I were starting from scratch I'd seriously consider going upmarket and trying to score a set of Braun/ads units. (ebay is a wonderful thing.)
pc