Hi XFactor,
Your description of everything from The Tempts to Journey leads me to believe that you're looking for a good variety of bread & butter type of sounds. This is a little bit of a tough call. The XV-5080 is nice, has great sounds and is very expandable. You'll need a sequencer as you said. The Triton is nice as well but may not give you enough of the bread and butter sounds that you need (the piano is not very good on it IMHO). For synth sounds, EP's, guitars, and strings it is quite nice. They both have strengths and weaknesses. You have to look at what is important to you.
If the Midi Data Filer works for you, why would you spend the dough on a MC-80? For playback only at live gigs, you really don't need a sophisticated sequencer - just something that plays back and does everything you need for live performances.
The Triton has the sequencer already built in and you can get a SCSI hard drive (only if you also buy the SCSI option but, if you want to use samples this is a must) to load in sequences quickly. I believe that it has a few performance features like if you want to chain songs together and so on. For samples, it depends on what you plan on loading in. If you load in lots of background vox and so on, you may need to spend quite a bit of time in between songs loading in some new ones. It depends on if you sample in stereo or mono.
If the Triton's sequencer is anything like the Trinity's you'll find that Cakewalk has better editing features but it should do the job for live use. Polyphony is about equal even though the 5080 is 128-note polyphony. I own a XV-5080 and I've run out of polyphony before myself. It's all about how patches are created. The Roland can have as much as 4 voices used up by a single patch (many use 3 or 4) while the Triton can use up as much as 2 per program (again, many use 2). So, if you divide up the maximum for each by the maximum voices used by a single program you get 32 (128 / 4) and 32 (64 / 2).
Both units sound great. You'll have to look at how you'll be using it to decide. If you will be using lots of samples, the added memory expansion for the 5080 may be what you need. If you'll be using a limited amount typically for a small number of background vox parts and a few loops, then you may look at the Triton as it will give you everything in one box.
HTH,
Fernando