By adding Sense 2.5 through the .cab you are taking an already slow phone that is running Sense 2.0 (TouchFlo3D) and then adding all this (like 30mb i think) on top of it which is bogging it down even more.
I think your best bet if you like the newer version of Sense is to unlock your phone (HSPL in HTC Imagio/Upgrades) and then flash a custom rom. It is very easy to do. To bad there are only a few roms to choose from now and only one active developer.
C'est la vie.
The mr1 upgrade is better than the original rom - if for no other reason you will have far more free space. As far as mods for the stock (including mr1) rom - they are out there but harder to find now bc almost every one is running a newer version of Sense (2.5 2012 or higher). The mods for Sense 2.5 are mostly incompatible with the older versions.
Good luck. Seriously -not sarcastically.