Build my own or settle for whats available?

[Kronk]

So i need some advice from you reefers... I am going to upgrade to an aquarium in the 40g - 60g range and i am wondering if its worth going to the effort of building my own or just settling for something close in dimensions but more available?
My wife and I have a baby on the way so realistically I wont be upgrading for a long time. Oh and the Mrs. has absolutely no interest in reef tanks... crazy I know...
My main concern is if I get a tank that doesnt have the exact dimensions I want, I will end up regretting not going with a custom. But honestly does 2" here or there make a huge difference? Budget is a concern as well...

Thanks,
Ken