You didn't mention what kind of gear you currently have. Ideally you want a separate pre-amp and amp with the 355 in between or an integrated amp / receiver with pre out / in loop, but if you have an integrated amp or a receiver with tape connections, you may still be able to use the EQ. On some older gear you can connect the tape out to the EQ in and EQ out to the tape in and use the tape monitor feature to run all signals through the EQ.
To be honest, EQs are not very big sellers any more. Most modern speakers are good enough not to require manual equalization, and when it comes to adjusting for room acoustics, a modern AVR with Audessey room correction does a better job. It depends on your own personal goal. Is it to achieve as flat a response as possible matching the source material, or is it to shape the sound curve to match your own tastes? "Sound quality" is totally subjective and some purists might argue that an EQ in the wrong hands will be detrimental, but in the right hands or with proper measuring equipment you can compensate for some of the room's characteristics.
"Reasonably priced" is also very subjective. There are plenty of people here that spend way more than I am willing to.
I would start with posting what speakers you are currently using, as that will have the biggest impact on sound quality. Poor speakers on new gear will still sound poor, while new speakers on some decent older gear could improve things. Also, is this strictly 2-channel for music or any plans to add a TV and surround speakers?