5.1 under 4k?

I like the Paradigm Monitor subs at $600 to $800. Front firing, which I personally like, especially for a carpeted room. Surprising sound in a small package.

Since you are used to Polk, you'd probably like GoldenEar, which is one of Polk's co-founder's current company. At your budget, you could get three SuperSat 60s for L-C-R ($2400), a pair of SuperSat 50s for the surrounds ($1K) and their Forcefield 5 subwoofer ($999). This all comes in around $4400. I've heard their sats with their sub (as well as the Triton 2 towers and Aon 3 monitors), and their products have a *great* folded ribbon tweeter and their satellites with sub sound really good for both music and theater.

The Apex sub of Monitor Audio is cheaper and better then the RX subwoofer. Most other sub's in this price range are a lot less fast in speed than the Apex Sub. I never sell the RX sub, go for the better and less expensive Apex sub. Next step go for an Onkyo Amp. You will hear how much more depth and wide it has compared to the Marantz. Drive and individual focus of instruments and voices is superior to Marantz. Why? Because the transformers they use deliver more ampères. I am surprised you bought the speakers this fast. Marantz can not give a deep and wide stage. That is why it is a 2-dimensional brand.

Bo1972 - you sound like a dealer. If that is so, you should identify yourself as a dealer and reference your company. That is pretty standard on Audiogon. Many people in the business post here, but you should identify that.

I think you made some good choices. I had the 2nd generation Silver S8's myself and really enjoyed them. I'm sure the newer version that you have will sound even better. Also, I think it was a very smart move to go with the better centre channel. I'm not too concerned with HT, but the one thing I see quite often is that the centre channel sometimes has a hard time keeping up with the main L&R channels.

As far as a sub goes, I would just wait a while until your speakers break in and you have a chance to get to know them. Doing it that way will make your sub selection easier.