lol, well a laptop is a very different beast
1600 memory is fine, I tend to use that or 1866 whatever is a decent price.
It is really down to how much space you have, how much grunt you want, and whether the look of a particular case has you hooked.
By the sounds of things your original case, a 7600, that Asrock motherboard and the 1600 ram would work for you for a good price. The rest is just trying to find an improvement
My wife and daughter both have Silverstone SG02 shoebox style cases which are uATX and just that bit bigger, but makes it nice and easy to fit a big graphics card in there and gives a wider range of motherboards to choose from. My daughter's machine has a Gigabyte board which was really hard to get quiet, so I tried a Silverstone SFX sized PSU which is tiny and runs fanless at low power when just browsing etc. I am not generally a big fan of Silverstone stuff, but those PSUs are lovely, and for £66 they do a modular one. They come with an adapter plate to run them in an ATX case, which in the SG02 makes for much more room for airflow.
For the last week or so I have been using an ITX CoolerMaster 120 Elite as my main machine with an old FM1 APU in it. That machine happily took my R9 285 graphics card, powered by a Novatech semi modular 400W PowerStation PSU, and it is visibly smaller than than the uATX SilverStone, but I don't feel it frees up much extra desk space.
But practicalities aside, the case is something you look at quite a lot so I think it is worth having something you are happy with. Unless you go for a full ATX tower like my main machine and hide it under the desk