AR magazines are 1/2 to 1/3 the price of .223 AK mags. If the Saiga was in 7.62x39 or 5.45x39 with cheaper & more readily available mags it would be a different story.
Anybody know from experience how the stag stands up against say an m&p sport, or compareable dpms? Worth $800 for what I am gonna use it for?
DPMS AR-15s aren't in the same league as Stag, nor S&W. I've noted it before, and it's a shame, because DPMS' LR-308 (SR25 / AR-10 type) show that they can build a better rifle.
This is my comparison of the Stag Model 1 vs. the S&W M&P-15 Sport, posted previously here on THR:
The Pros of the Stag are the chrome lined bbl, double heat shield handguards, dust cover, and forward assist. The cons are that you don't get M4 feed ramps, nor an HPT/MPI bolt (unless you spend an extra $100 for the plus package, which gets you those and a few more features).
The Pros of the M&P Sport are M4 feed ramps, HPT/MPI bolt, 1:8 twist (will stabilize heavier / longer bullets), 5R rifling (reduces friction, known for accuracy), Ferritic Nitrocarburized (Melonited) bbl (3/4 the wear resistance of hard chrome lining, without loss of accuracy), and lower price. The cons are lack of forward assist & dust cover, and unshielded handguards.
For me, the HPT/MPI BCG, M4 feed ramps, and Melonited 1:8 5R bbl were more important than having a dust cover & forward assist. I didn't care about the unshielded handguards either, because I knew they'd be coming off anyway. If you like standard handguards, shielded sets can be had from the big name online AR places for under $25. I've also owned an M&P-15 A before, and knew from that experience that their lower parts are good to go. For some, the feature set on the Stag may be more appealing.
http://www.thehighroad.org/showpost.php?p=7444070&postcount=17
Hope that helps.