Newer boot ROM will not make a difference whatsoever. I have several 2500s, all with the newest boot ROM, and some of my 2500s show 16 MB, and some show 14 MB. The difference, is that some motherboard revisions have 2 MB of DRAM soldered on the motherboard, and some don't. This however does not effect your ability to install the newest versions of IOSes which require 16/16.