I own a Xone:62 and am VERY pleased with it.
Awesome build quality, sound quality kicks it's concurrence behinds. And the 4band EQ is just sweet to work with, you won't like to return to 3 band after that...

I used the X-9 also, and it was a big deception. On paper it seemed this would be the "DJM-500/600 killer", well in my opinion the DJM will be the standard for quite another time.
Don't get me wrong, controls are pretty tight (unless they break or get stuck, which happened quite fast on the model I tested, and several other people reported several things. Keep in mind, it were the first mixers of the range, maybe it's only on the first production samples). The effects are nice, comparable to the DJM's, but now you have two samplers and two effectors that can work on each other also. The digital in and outputs are a very nice extra, and the MIDI control can be very useful also. Also tascam has made a big effort against digital clipping, they left enough "headroom", so you have a pretty big margin.
So it sounds a great mixer huh (except for the breaking stuff)? The parametric EQ is very nice, sounds good, and is effective. Pretty easy to use, and you can store presets.
But the EQ are also the biggest flaw of the mixer. I had my Xone already when the X9 came out, but the flaw would still hold me back from buying the X9. You see, there is some sort of nasty delay on the EQ. If for example you want to cut the bass quick, like any normal person you just would twist the EQ knob very fast.
When doing that you won't hear a fast frequency cut, but it decreases pretty slow. It takes about 1 second for the EQ to work as you wanted. Way too big delay for me sorry (and this is not a matter of first production samples...).

So what mixer to buy. Depends on your needs (my classic answer ).

What do you really want? You just want to have a rock solid mixer with the some of the best sound available this day? Go for the Xone.
You want samplers and effectors. Go for the DJM-600, or even better get a Xone and a separate unit (so you can model everything to your needs, I know it's more expensive, but I prefer to wait a little longer and make no compromises).
You want digital inputs or outputs. Consider Denon mixers.

In a general point of view the Tascam isn't so bad. I just don't like what they did with it. If you're interested in the X9, I'd suggest you wait a little more, and see what becomes of it.

A&H, No question about it.