I guess you've already read my advice in the other thread regarding router placement and the running of USB adapters. If there is not much that you can do to move the router, buying a new one is very unlikely to improve the situation, with the possible exception on a MIMO system.
Multi-in/Multi-out is not to be confused with boosted/pre-n systems; it uses three or more aerials to split the signal and - like pre-n - requires a proprietary adapter to make full use of the added feature. Danoh uses a Belkin MIMO router with a Linksys MIMO PCMCIA card successfully, though it is normally recommended that you stay within a brand to be safe.
MIMO may give you some improvement, but you should work to optimise your current setup (router placement, USB adapter usage, booster aerials perhaps) before committing extra to expense.