Jerry,
The 'quick-n-dirty' answer is that you would want an HF antenna for HF, 6 meter for 6 meter, and the same for VHF/UHF. I've got a feeling that you already knew that, right?
From there it's more a matter of what kind of antenna grabs you, what you have room for, and what you can afford.
In general, HF antennas are usually horizontally polarized, and probably a dipole. That's about the easiest, cheapest antenna, if you have the room for them. You can squeeze a dipole into some pretty odd places/shapes and they'll still work okay. Nobody said they would be the 'best' though.
For 6 meters, a 1/4 wave groundplane makes for a pretty fair antenna. Another one of those easy/cheap thingys. Same for the VHF/UHF bands. As the frequency gets shorter antennas get to be a little less 'easy' to make (if you're 'bent' that way). That yardstick need to be divided in to 1/16ths or 1/10ths of an inch instead of feet, sort of. Not really that difficult to do, just a bit more exacting.
You'll also find that on the lower HF bands verticals are sort of discouraged. Or, you'll put a ~lot~ more work into them than you would on the higher HF bands. Multiband antennas tend to be large if they cover the lower HF bands. That means more work in putting and keeping them up. Less so for the higher HF bands, but still usually not cheap.
I tend to recommend home-made dipoles. Mainly cuz I can't see paying the typical cost for one when they are just not that hard to make. A 500 foot spool of wire, a few chunks of plastic for insulators, and a few SO-239's will usually yield a dipole on just about all bands you wouldn't want a vertical for...with some left over maybe. Naturally, you'll need the appropriate lengths of coax.
If spending money isn't that much of an objection, grab an 'AES' catalog and knock yourself out! 'AES' usually is the most 'illustrated' catalog so is good to shop from. Where you actually buy the thingys is up to you. And, just like with any antenna advertisement, if it sounds just too good to be true, and if it costs a lot of money, it's probably too 'good' to be true - lol.
- 'Doc
PS - And if you should decide you don't like that '2000X, I just happen to have a Yaesu FT-7800a and antenna I might consider swapping for it. Might even throw in an 'organ donor' AL-80A. And a watt meter!
I'm holding my breath...