Been there, done that, back on NBU 3.4.  It was a bit of a challenge since we had to work it out from scratch and it took us 2 attempts.  You can not recover the catalog - lots of end-of-line issues - and you may be changing master server names at the same time and that also creates a few additional challenges.

My recommendation is that if you can afford it, bring in Symantec Professional Services.  They've done this multiple times and should be able to make this relatively painless.  Symantec Customer Support will not support this if you do it on your own and run into trouble - this support policy is documented in a technote if you need justification to engage PS.  Once it's all up and running properly, they'll support you later.

If you do decide to go ahead on your own, you better be really good.  You must like/tolerate doing hex dumps of some of the files to see what's up.  If you have files >2GB, be prepared for some additional challenges since some of the Unix tools don't like large files (they may now on Solaris 10 but didn't when we did our migration on (I think) Solaris 8).

Break the process down into as simple steps as possible - do your upgrade to 6.5 first and then look at moving the EMM server to a dedicated system (I think this is a supported operation) so it's out of the way while you're doing your master server migration.  Worry about LTO-4 and disk later since your goal is to minimize the number of changes at each step so you can back or at least know where the breakage occurred.  We got most of the way there, backed out, and completed it later when we identified where it went wrong the first time.   The last thing you want is to have catalog entries in your new catalog and have to revert.