When to get new ECU

Here's my problem. On my 96 Civic EX, I have put 2 1/4" Pipes with Flowmasters Exhaust, AEM Intake and Polished headers. I plan on making some other changes like flywheel, clutchplates, etc.. but when should I change my ECU? Should I wait until I get all of my new parts so i can program it for them or should I get it now? Also, any idea on what the best brand to go with is? please don't say Spoon, can't afford it! Thanks.

JT