I am another HT newbie. The center piece of my HT is an SVS 20-39 PC+ tuned to 16 hz. It is just wonderful. But I have not compared it to other subs. I had a tiny squeeky kef sub before. I demoed the Q150, and some other lower range stuff. Have not heard anything approaching the PC+. I have had it since last October, and cannot be happier.
I recommend the PC+. Excellent product and excellent support. Ron and Tom walked me through every bit of the setup and decision. They recommended the 25-30 PCi, but I opted for the PC+. I could not go for the lower one, my ego did not allow me to do it. I have not looked back since.
One thing to note though, is that if like me you have not listened to real bass before, the sub will sound strange untill you get used to it (a couple of days). I was used to the bass boom from the kef and was prepared for this to disappear. It took a couple of days for me to appreciate what the SVS can do.
Another pointer is the voltage. The voltage is not automatic. It is set at the factory, so you have to make sure that they know what is the voltage you require. In my country, Oman, we use 220 volts and I specifically asked about this. I asked Ron from SVS whether there is a switch on the back for voltage levels. He informed me that it is set at the factory. Right before shipping, I asked Erik to test the sub properly before sending it to me. I also enquired how he can do the testing since they have different voltage in the states. I was told that they have a circuit of 220 for non-us customers.
I hope this helps.