The m17x is a premium product for Dell so it rarely goes on sale although sometimes you see preconfigured models here at logicbuy http://www.logicbuy.com/Default.aspx They are usually configured one way at the sale price. I custom ordered mine direct from Dell but opted for the fastest CPU and GPU available with high res monitor but there was a discount on the GPU at the time for 580m. It is extremely fast especially if you get the SSD.
If i may ask, why buy a lambo to do a trucks job? There are many other custom brands that are just as good if not better that are cheaper and offer more options. Nothing wrong with alienate if you want to spend the money though.
Also a ssd will not affect gaming performance or gpu performance.
I'm not sure if you have read any reviews but for build quality, parts options, performance and features it is hard to beat the Alienware m17x series. An SSD won't help gaming but it helps everything else. With mine I configured it with a 256GB boot drive and used the 500GB it came with as a storage drive but you could easily put two 256GB SSD and raid them if you want to go extreme. Even though they are expensive, for performance and options when compared to lets say a 17" Macbook Pro, the m17x will easily outperform it and come out cheaper.
You will get no added performance from an alienware laptop. Build quality on laptops that would offer very similar hardware will be just as good and if they are not then its a matter of the quality showing up after the laptop is out dated.
The alienware laptops only look cool and are nothing more then a fancy shell with easily obtainable parts.
Just in case you are interested, it seems Dell is prepping to release the Alienware M17x R4 based on the upcoming Ivy Bridge CPU with Radeon HD 7970M and NVIDIA GeForce GTX 660M or GTX 675M as graphic options. Not a big surprise really since the both HD 7000 and GTX 600 has recently been released and Ivy Bridge CPUs are expected to be released on April 29th.
4GB of RAM is fine for gaming. To get a general idea of how the nVidia GTX 560M and AMD Mobility Radeon HD 6870M perform you can click the following link and restrict the results for those two cards. Note that only the GTX 560M has been benchmarked and is probably ranked higher than the HD 6870M based on specs since there are no benchmarks for the HD 6870M.