The 746, now discontinued (as are the 756 and 756PRO), is probably the most bang for the buck. It covers 2m as well as 160 through 6, and is quite a performer. The original 756 was not so spectacular, and the 756PRO improved many of the 756's shortcomings.
While the 756 family has really caught on and is very popular, many probably don't remember that the 756 was introduced to be a low-cost alternative to its big, older brother, the IC765. The 765 is rather spectacular, as is the 775 which replaced it. In terms of features and performance, the 765 or 775 blow away the 746 and 756 (and 746PRO, 756PRO, and 756PROII), but then they both cost quite a bit more as well.
The IC765 and 775DSP also have built-in AC power supplies (standard, not an option) and the 775 model runs 200W PEP output, like the Yaesu FT1000D and FT1000MP-MkV, which are its only competition.
I'd recommend you visit a dealer if possible to "test drive" these rigs and see which one suits you best. Even if you intend to buy a used rig, trying out the "new" version is very useful. Sometimes it's the small things, like knob position and feel, or display color, that makes a rig comfortable for the user.
Since I use CW, SSB and AM (!) on HF, I am very picky about how easy the rig is to change operating modes, get going and sound good. If one changes modes, power, CW speed and other things very frequently as I do, he is likely to shy away from rigs having mostly menu-driven features that take more than one button press or knob twist to change. I also favor only transceivers having a good, functional MONItor which allows me to hear how I actually sound on the air via my station headphones. Many rigs don't have this feature, but it's an absolute must for me.
73 de Steve, WB2WIK/6