How do I know if MY system has good speakers?

[CptGreedle]

I am using JBL speakers for the main left, right, surround left, surround right, and I plan to upgrade the center speaker this year to a nicer JBL... but all the other speakers and the subwoofer came from a Yamaha 5.1 surround sound speaker system in-a-box (there are a total of 9 speakers and 1 subwoofer). I don't know how to adjust the subwoofer, or if it is even a good one. It all seems to have good sound to me, but I am always willing to get something better. I noticed a big change when I upgraded the speakers to JBL, but I am not sure how much better it is.
The main JBL speakers are bigger than the others, and until I upgrade the center one, I don't plan on upgrading the others for a long time. I have hooked up 2 back speakers, 2 presence speakers, in addition to the center, left, right, 2 surround speakers, and the subwoofer.
The entire system has been optimized by a professional who used a pro-mic and various other settings as well as some demo discs. I think he did a great job for what we have, and until we can get the speakers in the ideal positions, the locations right now are decent (the surround speakers are a little below head level, rather than above, but I don't own the house and can't hang the speakers without permission).
http://www.yamaha.com/yec/products/p...9&CTID=5000800 These are the Yamaha speakers I am using (not the receiver, i have a better one than that).
http://www.jbl.com/ And these are the JBL speakers.
For the price, I got what I think sounded best, and had a good name.
Any comments?