The TBS6983 is no longer in production, if you are lucky enough to find one second hand in working order snap it up. It was one of the best cards they ever made in its day and is good today apart from no S2X. The TBS6903 which was the successor to the TBS6983 is still in production as far as I am aware, there are suppliers out there with it. If bought new, the TBS6903 is not a card for two bob merchants, it aint cheap at around £300+. I saw one go 2nd user on eBay a while back for £150, a real bargain.
Unless there is S2X or Novelsat guff that you need, I would steer clear of the TBS6903X card. It is slow to blind scan with Windows apps.
Under Linux, the TBS6903X comes alive when used with nuemodvb,
@satesco has had some really good results with it. Again, it is not a card for tight wads, it is another £300+ job.
For USB, the TBS5925 is OK but no S2X and it runs hot, it still works though. The TBS5927 is just a TBS5925 with an internal fan to cool it, again no S2X
If you want S2X on a TBS USB device the TBS5930 is listed as doing this and it is cheap.