Would a
Q200C or Q600C be within his budget? If not, then you could try one of Dennis Murphy's Affordable Accuracy center channels. I believe he sells them for $120 + shipping?
See this page for contact details. He doesn't have the center channel on his website, but on-axis response should be reasonably similar to the
AA monitors, which is to say, flat. Which is to say, having a neutral character. He starts with an Andrew Jones designed Pioneer center (the SP-C22), then upgrades the tweeter and crossover.