Stocks are such a personal choice, me giving advice would be opinion only. My Rem 700 .308 has the factory HS Precision (pillar bedded) stock it came with. I have three 700s in centerfire and another as a muzzleloader. Each has a different type of stock, none are adjustable. I don't change much so I don't really feel the rifle needs to be adjustable. Like I said, it's all opinion. Is there something about your factory stock that you don't like?
I think the cheapest stock out there with adjust-ability is the Choate Target/Tacticals $150-$200. The Accuracy International Chassis System (AICS) are towards the top cost wise $900-$1100.
Here's one I'd like to build another long range rifle on:http://www.brownells.com/.aspx/pid=43777/avs%7CMake~~Model_1=Remington__700/Product/REMINGTON-700-TAC21-CHASSIS#
Right after I hit the lotto... LOL