First bike build, and i've got a couple of Q's

Hey everyone, as you can see I'm new here. And I'm researching what i'll need for my first bike build.

Criteria is as follows:
Cheaper Build, but no corners cut.
Perform as a robust daily commuter,
Be rideable on dirt tracks, rutts, etc. (not jumping it)
Front/Rear discs
Front/Rear suspension (though rear is looking less likely as most cheaper dual sus bikes lack the room in the frame for mounting)
Shift Kit to improve ride-ability
Rubber mounted engine to improve NVH

The only things I know for sure i want to use are as follows:

The RockSolidEngines.com.au 200watt engine kit.. to keep things legal in my state. (may or may not stay legal though
The SPB HD shift kit
Megarange 11-34 Shimano 8 Speed Cassette
As as for a frame I'm really not too sure.. One of the Atomik hard tails that pop up on ebay look fairly suitable?

What are you thoughts/Suggestions?
What other obvious things am i missing?

Thanks a lot guys any input would be appreciated,
Ashlin.

Thanks for the heads up, hard mounting will be tried out first, and if i'm not happy with it i might play around with other things at a later date. Can you recommend any cheap Chinese bikes that have dual suspension and discs with room for an engine?