First, so we are on the same page here... is this your PC?
http://www.newegg.com/Product/Product.aspx?Item=N82E16883113161
If so, a GTX 970 will work and will fit, but your PSU will need to be upgraded. The GTX 970 is a 145W card at the very least and requires a high quality 500W PSU (or better) with 2 x 6-pin connectors.