Well I don't see major problems with that loadout and as for the should you take the internal HDD or external, I'd go for the internal, it's just more handy and might be faster in data transfer (dunno how it compares to for instance USB 3.0) I think the newest trend is to have SSD and HDD, put OS to SSD to make it run more fluently and use HDD for storage.
And for the GFX card GTX660 isn't that miraculous (I have in fact 660 too altho I paid 260€ from mine you found it cheap lucky sob) I'd probably choose a more powerful and more in-line card with that setup.
You won't need that much RAM (if you aren't some kind of hc video editor etc) but if you got it foor good value and it suits your budget, why the heck no
