well the 746 and the 7000 sound nearly identical on air.  I am guessing that
they have very very similar audio circuits in them, if not identical.
They have that particular boomy audio which has the ability to cut through
pile ups....I believe its a low mid boost that is built into the audio
circuit that does it.
It doesn't seem to matter what sort of microphone is being used, it still
has that distinct 746/756/7000 audio to it.
That said, the ts2000 with a heil on it sounds like a studio quality set up
by comparison.  Yes, the icoms have a good boomy audio that cuts through,
but if you use the narrow setting on the heil with the ts2000, you can cut
through just as well, and on wide, it sounds like a million bucks compared
to the icoms on air.
just my opinion.
I haven't played very much with the 756 or 46, just briefly with a 756 of
one series or other and I really didn't like the receive quality, however,
that could have been a filter or band pass setting that I couldn't adjust
from the front of the rig.  And they're huge radios as well.

The ic7000 on the other hand, was pretty close to the ts2000 as far as that
nice wide band quiet receive that you can get with the low cut and high cut
set to the lowest and highest limits.
So, if a person was going to look at getting a new HF radio, and didn't care
to much about dual receive or having allot of settings right on the front of
the rig, the 7000 is perfect....since it also has the speech synth and voice
recorder built in.
Its the size of a typical camercial VHF radio too.
And, the front pannel, that can be removed if desired has the microphone and
phones/speaker jack on it instead of that goofy setup like kenwood has.
If i were to ever be able to afford another rig, it would be a 7000 hands
down for so many reasons.
A note about the 7000, many folks seem to think it is a enhanced 706, it
really isn't.  It is very much its own animal and is, in my opinion, much
supperior to the 706 mark II g in many ways.  So, there really is no basis
for comparison between the two other then they are both made by icom, and
they are both multiband radios which are small.

That said, the ts2000 offers everything the 7000 does with the extra $150 or
so for the speech chip and voice recorder, and offers all the functions that
are necesary that the 7000 doesn't, like talking menus, dual receive, high
power output on VHF/UHF, 1.2 gigs if you want it, more user friendly
controls on the front which can be set manually instead of through menu
settings, and probably a bunch more that  I can't think of right now.  And
the price is coming way way down on the ts2000's right now as well.

73
Colin, V A6BKX