You could have a look at the Reloop ADM-5. If the specs are true, they go relatively low for a 5″ (39Hz, where others often stop at 50 or even 60Hz), 2x 30W RMS (not powerhouses, but you don’t need them to blow your brains out after all) and tone control (not needed imho, but I know people think about that differently).
Reloop has opted for an active/passive combination. While this combination does have drawbacks, it does make a lot of sense if you want to keep the cost down. Effectively it saves you one amp.
Mackie CR4s are an option, but 4″ so they stop at 60Hz
M-Audio BX5, although at the high end of your budget (or even over)
That kind of money is just not gonna get you anything really good. The KRK 5s are considered a good entry level monitor and even those are almost 200 bucks EACH.
The speakers I mentioned will get you a lot better performance than any 2.1 or 5.1 system, but that is not saying too much.
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