X5 is the only nine-speed system that SRAM currently make, and with importers Fisher Outdoor not bringing the chainset into the UK, it can be hard to find. This does leave other options, and the ‘10-speed’ X7 chainset worked perfectly with the supplied nine-speed chain and front derailleur, as did Shimano's Deore chainset.
Glancing at the parts you can see that the groupset lies lower down in the SRAM ranks, with a more basic approach to design such as the drilled cassette and single clamp shifter pods. However, most of it is not that heavy, with the PG951 chain seeming more robust than 10-speed offerings, and gets a bona fide Power Link for quick fitting and removal. Shifting is muted with a noticeably less fluid shifter feel, but gets the job done. Often you simply forget there are ‘only’ nine gears out the back.