Since your amplifier is still working fine the 1446 final is a great final. I would not mess with it. Even if you blow the pills I would still replace them with the same or the HG version.
Unless you have a good local amp guy your never money ahead swapping out to larger finals. There are other things that need changed and re-worked. As already stated the cut out in the board for the 1446 final is smaller then what's needed for a 2290 or 2879. Even more work would need done.
If you need MOPOWA I would sell it and just buy a bigger amplifier.
1446s had a reputation for having more modulation than the 2879s but less swing than the 2290. Correct me if that was not the "rumor" during the early 2000s or do I have it backwards? Easily get 250 PEP with two of them.