Thinking of maybe adding a subwoofer. Sony STR-GX10ES receiver with pre-outs Wharfedale Diamond 10.2 mains Budget under $300
I don't see a dedicated sub output unless my tiredness is preventing from seeing it. In that case, you'd have to plug it into the same speaker input as your Wharfedales and set the appropriate crossover on the sub itself. Do you absolutely want to buy new or are you OK with used?
I'm looking at the Andrew Jones Pioneer or ELAC subs. I'd use the pre-outs on my receiver and use the crossover on the sub for below 60hz. I'd run the Wharfedales full range. Otherwise I am looking at just getting some used big speakers like: Polk RTA 12B DCM TF500 Snell Type E II AR AR92