Best speakers for Pioneer SX-1250 receiver

i like the ads recommendation above--try the 1290, 1590, etc. alternatively, acoustic research of the same vintage

Actually Thiel CS2 thru 3.5's would sound great with your Pioneer - I know from experience with my SX1050. My gf now has it with a pair of Meadowlark Kestrels - all purchased used here on the site. I love the Pioneers. 

ADS as well. Had those with a Marantz 2250b receiver. I've avoided "vintage" AR's and the like simply because most of them appear more compromised than the others I've mentioned, and purchased. Klipsch Heresies sound great on the old receivers as well. 

There is some thinking that the old receivers sound "old", but to my ears they simply sound different. Any piece of equipment that's 40 years old and still sounds good deserves respect!  Good luck!

I went to my tech with my SX1050 to see if he could put an iec to replace the wimpy stock power cord and he said it wouldn't be worth the effort. There just isn't the room sufficient to cut and modify the back. He replaced the power cord with a newer, slightly beefier cord and all has been good. Keep it as stock as possible!

Klipsch Heresies would really rock (as oblgny stated) but might sound brittle at high volume. I would try them or maybe a pair of Bose 901s on stands. That would be a fun system. BTW I had the 901s and the equalizer help smooth out the freq band in the room.

Two things. First, make sure it is recapped, or you will be playing Russian roulette with your speakers. Don't bother changing the power cord, unless it is damaged. Second, beware of older speakers. Speakers do age, and not just the capacitors in the crossover network. Cone surrounds in particular will often have dried out.