I've got a couple of 660's, in 350 Mag and 6.5mm Mag. They are great little guns. Most folks consider the 350 to be a heavy kicker in the 6 1/2 LB 660 (6 1/4 in 600, shorter bbl), but for some reason the stock fits me pretty good. I don't find it kicks too bad. I'm 5' 10". My 6' 2" brother in law shot it and got a Weatherby eyebrow, so I suspect the gun fits small to medium sized guys best. The dog leg bolt fits in a saddle scabbord nicely, but some folks think it's ugly.
I've killed moose and deer with the 350 Mag. It was perfect for moose, and lets the steam out of them with authority. With deer, it's just too big, and leaves too much blood shot meat even with a good rib cage hit. The 350 is easy to reload for with 200, 225 and 250 gr bullets in several choices. I shoot Hornady 250 gr round nose and Speer 250 gr spitzer. Just make sure you choose a bullet that is fairly short, both to stay within the magazine box (2.8") and to not exceed the capability of the 1-16" twist in Remington firearms. Brass is available in Remington bulk. IMR 4320 is a great powder, although I'm about to experiment with WW 748 and Reloader 15 this summer. With 4320, it shoots under an inch every group. With factory ammo, you can only buy 200 gr, so it is somewhat limited in usefulness if you don't reload.
The price of $900 is actually pretty decent for a 660 or a 600. I paid $750 about 10 years ago for mine. The 600 has an 18 1/2 in bbl, polished bolt and a plastic vent rib, while the 660 is identical but has a 20 in bbl, blued bolt and no rib. If $900 is too steep for a used gun, Remington chambers the 350 in it's 673, a modern day model 7 based copy of the 600. The new Model 7 CDL is also chambered in 350, as is the Ruger 77 stainless. The new guns a cheaper, and will go down in price with age. The 600 and 660 cost more, but gain in value with time. The 600 and 660 have a light weight but flimsy trigger guard/floor plate, which can be replaced with blued steel aftermarket for about $100. I'm holding my breath for a Model 7 stainless in 350 Mag.