I would recommend the Polk Audio setup that was linked above. However I would recommend this Yamaha sub instead of the Polk Audio sub. It has a much better frequency range (on paper). I've never personally heard it, but if the specs are accurate, it's a better sub.
Honestly in the $100 department that you have left for a subwoofer, the choices are kind of slim really. I personally think the Yamaha would be the better sub. I definitely would recommend those Polk speakers though. I've heard them at BB, quite clear .
Just looked up your receiver. Wow!!! That is one VERY nice receiver! 110w RMS x 7 @ 8ohm, and TONS of features. My next receiver's going to be expensive .
It's 22.5lbs, so 110Wx7 is a little optimistic. The majority of a receivers mass is the amplifier and heatsink. The added size of a heatsink and power supply necessary for that spec would most likely put it somewhere around 40lbs. In reality it's probably closer to 70Wx7.
I have the identical Polk Audio setup Mikecdm suggests; every last speaker is the same. (The difference is mine is ran by a Denon AVR-1910 with 16Ga wire instead of the Pioneer VSX-1020-K.) The speakers have a very clear tone with an even sound field in my experience. They sound best when you have the changeover around 60-70 Hz, anything higher and the center channel starts to become too bassy to clearly understand speech. My amp can auto adjust the levels (if yours does not, I recommend a decibel meter and a copy of Digital Video Essentials (in fact, you should get anyway to calibrate the video, but this does sound too) for maximum quality.
If it helps any (and it likely will not since your room will differ), I have the sub set to its maximum crossover with the volume around 40%. The amp then sends signal to the sub at Â±0 dBA, and the speakers from volumes ranging from -3 dBA to -9 dBA depending on the channel. The sub gave me its best response with an inverted phase, but that will really depend on where in the room it is in relation to your other channels. Put out a constant pink noise around your crossover frequency, sit in your prime listening position, and have someone flip the phase switch forward / backward until you determine which has the greater bass response.
If I had the money myself, I likely would have bought that 12" one instead of the 10". I had thought of downgrading the fronts from Monitor 40s down to Monitor 30s to make up the difference, but in the long run, I thought the sound field would be more balanced to pair up the Monitor 40s with a CS1. I did test the Monitor 30s with the CS1 solely, and then the Monitor 40s with the CS1 solely, and I cannot say I made a bad choice. If you have the extra $150, by all means go for it. (The 12" is rated down to 23 Hz, the 10" is rated down to 35 Hz. In my testing, Bass Mechanik down to about 28 Hz works, so you would expect the 12" to hit the high teens.) If you must give downgrade the Monitor 40s to 30s and/or give up the CS1, I say pass on it.