I personaly would just go filterless if you cant go with a sump. If your doing a reef tank, the rock and sand bed if your using a sandbed will go along ways. A skimmer that hangs on the back would be a better choice then a hang on the back filter. Again your talking about not spending much. So that would be out depending on knowing what your limit would be. You dont need alot of fancy filters and what nots to run a successful reef aquarium. HAVE DONE IT FOR YEARS MYSELF. Just spend time researching and reading and asking questions like this one. Water parameters can be kept near perfect with only good husbandry and dedication...water changes , stable salinity and temperatures and compatible inhabitants based on your experience and lighting and flow in your tank. Just put enough sand, live rock and some powerheads in it and it should workout fine based on the above mentioned things. In my opinion most external hang-on filters or canister filters just turn in to nitrate/ammonia/algae growing phosphate factories unless you keep up your mantainence on them which most people dont.
