i have no experience with the roccat keyboards however i do know the mice are well liked and respected so would expect the same to carry over. your choice on this one.
honestly just about any mousemat works. even $5 cloth mousepads will work though some of the larger gaming ones are fine as well. most mice work fine on flat black though some may work better on colored surfaces like the razer pads use but i think this is a rarity.
i have not used the g402 but i have used the g502 proteus. good performing mouse with easy to use buttons. was a bit narrow for my liking (deathadder fits me better, or kone) and the scrollwheel was not so nice (but if you like hyperscrolling then you would love it). build quality was pretty good. i expect the g402 to be similar.
as someone who has experience with both high end IPS monitors (no low end e-ips here) and TN panels i can certainly say that good ips monitors will have quite a bit better color accuracy (bit depth... difference between 6bit and 8bit basically) though will be about twice as expensive as typical tn (not talking about the 144hz models here which are pricey). the viewing angle is also much greater on IPS over TN without distortion such as greying out or color inversion if viewed from an angle (better on some newer TN but still not excellent). IPS however is only 60hz. generally many so called pro gamers will suggest 144hz monitors and claim that they are better and smoother and in some cases they are correct however the average person does not need to spend the money (twice that of normal TN) or need the performance (which needs better hardware to provide the sort of framerates to make it worthwhile). if you wanted low cost a standard 60hz panel is fine. you might want to look not just at TN but also at VA/PVA which may offer a slightly better viewing angle. i know brands like dell, acer, asus, viewsonic and samsung are good. not sure how good the benq is and would suggest reading some in depth reviews.
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i can say what i personally like using for peripherals in case you wanted ideas. i dont expect you to like the same things i do. (photo in sig link)
-i use my 40" sony bravia tv for gaming since it is rather large and i already have it around for movie watching. my old screen was a viewsonic vp201b 8bit s-ips screen which worked wonderfully and i loved every moment of it (should for the money paid for it!) when i used it before.
- razer deathadder mouse (fits my palm grip style and the need for a large mouse).
-razer tartarus (for when a keyboard just will not work, though i prefer using keyboard)
-model m keyboard (ancient board but love it anyways, not suggesting just saying what i use). i liked the wasd mechanical board when i had it as well though not impressed with how the cherry keyswitch design handles accidental spills. good if you dont spill into it. logitech also ranks up there in my book and the membrane keyboards i've had from them have lasted a long time. right now i'm on a cruddy $5 keyboard which i do not reccomend. its worth spending a little cash for something quality.
not sure that what i use helps, just thought i'd list what my preferences are in case you wanted to use the info to judge my suggestions above to see how similar our taste is.
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