...which is another way of saying that I don't know this first hand:
Dive Rite came out with the Transpac back in the 90's and it enjoyed substantial success. As is the case with many manufacturers, Dive Rite was actually badging a BCD manufactured by another company, which actually owned the rights to the BCD.
In steps ScubaPro, which purchases the company that owns the rights and manufactures the Transpac. Voila, the X-Tek is born. Dive Rite scrambles and comes up with a new/improved version, which they call the Transpac 2, along with a new manufacturer to actually produce the things.
I don't know exactly how true the above story is, but anyone who has ever looked at the old Transpacs will see that they are virtually identical to the old X-Teks. Both the X-Tek and the Transpac are out of production and have been for some time. The newer versions, called the RecTek and the Transpac 2 represent varying degrees of changes over their predecessors and they won't be mistaken for each other upon close inspection.
I own one of the old X-Teks and like it, with reservations. It's comfortable, works well with singles and is okay with light doubles. It makes a pretty good piece of travel gear for warm water reef diving, but falls short for anything remotely approaching technical diving. I also had problems with the velcro on the tank bands failing after about 75 dives. Since the bands aren't changeable (one of the improvements SP took care of with the RecTek) it was a PITA to deal with. SP came through for me and fixed it even though it was out of warranty, but it took time to do and was a hassle.
I use a backplate and wing for most of my diving, which would be my recommendation. If you like the softpack and the semi-technical features of the X-Tek, you're options seem to be limited to the RecTek, the Transpac 2 and the Zeagle Ranger. All three are decent devices made by decent companies.
Steven