Your music choices don't sound very bass heavy to me. And, you live in an apartment. I'd suggest dropping the sub for now and adding the difference to the mains. Also, I think you'd be better off saving more for a bigger sub and adding it after extended listening and determining what it is your set up lacks. Some good mains will cover the sub frequencies anyway (for a small sub).

If Jazz and Classical are significant in your listening, skip the monitor series and try to swing the Studio 20's or even better the Studio 40's. Your ears will thank you in the long run. I have the 20's and although my sub does add something, I could easily live with out the sub, especially for Jazz and classical (although my tastes run to chamber and not orchestra). The Studio 40's would be welcome.

I don't know about Yamaha being soft in the bass. Perhaps. It never bothered me. Seems like an active sub's amplification would cover any lack in the receiver. In my opinion, the receiver isn't doing much more than just passing the signal through. And for bass in the mains, you'd want to get more sensitive speakers for a low power receiver...