$400 pre-amp/proc or wait awhile

My wife & I have our first two children on the way & of course, a limited budget. As luck would have it, our pre-amp recently broke on us. I have been researching HT and figured I would accumulate components one at a time. I currently have good front (Vandersteen 2ci) & rear speakers (Frieds) and a good 2ch amp (Adcom GFA-555).

Since I need a new pre-amp, it seems like that's the next piece to get, but it also sounds like the technology on these advances much faster than the other components.

Am I better off waiting on the proc & either fixing my current one or buying a used 2ch. pre-amp to tide us over, OR can I find a reasonable proc that won't be outdated by the time I assemble the rest of the system (~2 years)? We have about $400 to spend right now...maybe up to $600 later. I wouldn't want to invest more than $200 in a 2ch pre-amp.

One other question, are both DD & DTS essential? Given my budget I am tempted to get a better quality component without that might lack DTS.

Any thoughts or recommendations on specific pre-amps or processors would be appreciated.