I have a bluetooth phone, bluetooth card in my Zaurus and use a Bluetooth GPS unit.
All work well together. Used to use the last Bluetooth phone with my PC as well, and though fiddly to set up, that used to work fine as well. Not got round to setting up the new phone software on the PC yet.
But Bluetooth failed technology... Just a tad strong.
Anyway, one thing worth considering in deciding between CF v BT GPS unit. How you intend to use it.
e.g.
If you tend to use the device landscape, then you tend to find it pointing the wrong way for a CF card.
If you are out hiking, might find it more hassle carrying 2 seperate units if you go for a BT card. Stick it on the backpack ?
If you use in a car, then I find it quite nice being able to leave the BT GPS unit on the dash (good GPS signal) while using the Zaurus.
I found with GPS units, having them close to the windscreen makes a big diference.
With BT unit, not a problem, can pick up, put down Zaurus as I wish. With CF unit, you would probably be fixed in one spot.
My big issue at present, is I have a mounting kit for the C860 which mounts horizontal, so rules out a CF card for me.
By the way, tried all the units on our site and they work fine with the Zaurus Cxx models and the 5500. Not sure about the 6000, but can't see any reason why they should be different. Especially BT, since you are just using Serial profile.
So Haicom MMF, Holux BT and GlobalSat BT should be ok.