Help me complete my home theatre for $300

Long time lurker here and really appreciate all the info on these boards....helped me greatly in purchasing my present setup.

Here's where I'm at presently for my 13'x13' room with 9' ceilings:

Items that are newer and will be sticking with...
- TV: 50" Panasonic Plasma
- Blu-Ray: Sony BDP-S370
- Receiver: Onkyo HT-RC160

Items that are older that I can keep and incorporate or upgrade as needed...
- 2 front tower speakers: Phase Technology 5T (6.5" woofer, 1" dome tweeter)
- Powered Subwoofer: - M&K VX-7 (8" woofer, low pass filter goes from 50Hz to 125Hz)

So, where I'm at is I have $300 more able to spend and want to get the best bang for my buck. The obvious thing that I'm needing is a center channel and back speakers to complete the surround sound. Want to get all of your opinions on my best possibilities....add to what I already have or just scrap the present speakers/sub and get an entirely new 5.1 system?

The receiver does support 7.1 setup and the HIIz (Height) feature....having speakers on the sides isn't something I want to go with, but could go with the 2 front height speakers if that's something you guys suggest.

Thanks in advance for help and if there's any other info you need please let me know.

Through Craigslist I have the opportunity to purchase the 5 Energy speakers (no subwoofer) linked below for $180. Good deal that would work appropriately with my present setup or not?

http://reviews.cnet.com/surround-spe...html?tag=mncol

Thanks for the thoughts Ron. I guess where I'm at is I have nothing to base comparison off of if my present Phase speakers and M&K sub are good or not.

They are about 7 years old and I acquired them from my father and have been basically sitting in storage for 5 of those 7 years....so in perfect shape still.

Are the Phase speakers and M&K sub solid pieces that I can build around?