All depends on your personal preference. There are cylinder and bay reservoir combos. Have a look at the
XSPC D5 Photon 170 and the
XSPC D5 Photon 270 as well as the
Monsoon Series Two DDC or D5 variants.
Both D5 and DDC pumps are the standard, not just D5s as stated before. DDCs have better head pressure than D5s but D5s can be a bit more silent at certain settings. I like both reservoirs I linked and know it is beyond your budget but if you can't flex that much, than I would advice looking at a
MCP-50x pump w/ a cylinder reservoir from Swiftech. This should be right on your budget.
I personally like the Monsoon Series Two because it comes with two silver bullets for your biocide of the loop and built-in LEDs in the reservoir as well as being a bay reservoir. XSPC is great for those that like cylinder reservoirs and also comes with a LED as well. It all comes down to personal preference on how you want to route your loop and look. One is not better than the other, etc.
Hope this helps.