I rode my 725tr with the aluminum fork that came with it on 42mm deep rims for 2 years. personally i liked how stiff it all was and didn't think it was too harsh. I just recently changed the fork out to a used carbon Alpha Q fork I bought off ebay for $80 a while back. The difference is noticeable, although minimal.
If the new frame comes with a fork, just ride that one. If you decide you want to upgrade after a few months, then you can do so. I think too often people buy new parts without reason, like getting a pair of weinman rims to replace the stock rims on a BD bike. That isn't an upgrade at all and still cost $130