I have the M14x. The SSD option is a Samsung 830 series. In other words, just pick the cheapest hard drive option you can find, and then buy the Samsung yourself.
Yes, the loading time of anything will be significantly improve. I play D3, L4D, TF2 and CSGO on my laptop, all on the highest setting. I also will be playing the upcoming FF14 when it is out.
Use coupon QMLNCPHHBMDF1M to save $100.
http://www.dell.com/ca/p/weekly-deals-2?~ck=mn This model becomes $1199.99+tax.