Splicing on a HT to 2channel system, best approach

On 8/18/05 I started a thread asking which center channel speaker should I use between my Vienna Acoustics Mahler speakers to begin putting together a 5.1 home theater system.

This is my current 2 channel system:

System components:
CD Player, Meridian 588
Preamp, Jeff Rowland synergy 2i
Poweramp, Classe CAM 350 monoblocks
Speakers, VA Mahlers
DVD Player, Sony DSP9000ES
Piano DLP Projector
Daylite 7' front screen

I am now asking a broader question and seek guidance as to what approach I should take in systematically "splicing on" the rest of the 5.1 HT equipment. I cannot afford to purchase everything at the same time. My 2 channel system will stay pure and not go through the processor.

Question: In what order should I buy the necessay equipment to get the best impact in the movie experience for the dollars spent?

For example I could buy a processor, then subwoofer, then center channel speaker, then L/R rear speakers.

Or I could...........any help would be most welcome.

Thanks