I'd check with Mile High Shooting first. I've heard the Butt spike kits were over $300, not sure if thats true, but just what i hear. I just got back from shooting my 7wsm in my new AX chassis. It performed great off my rear bag. I'll be using it until i can pick up a used butt spike kit on the cheap.
I like mine, the pistol grip felt odd at first to me because I leave my thumb on the same side of the stock as my trigger finger. But after dry firing it for a little bit it isn't so bad now.
I bought mine with full intention of hating it and reselling it. However, that just isn't the case now. I really like it. It's alot "tougher" than I expected it to be. I love the amount of adjustability. I shot mine today and did very well with it. I'm happy overall. I wouldnt have any fears in buying one. If you didn't like it you can easily resell it for within $50 of what you paid for it. Get the FDE color if you can as that's seems to be the "latest fad" and if you don't like it, it will prolly sell alot easier than the OD green.