I'm a firm believer in going for one that has been developed/specified by a Saab specialist.
So I'd go for either the Abbott Racing, Maptun or Speedparts/Elkparts one, because you know they are 99.9% bolt in replacement of the original.
I and a couple of others have a custom made unit from Allard. It is 50mm wide which I am sure is the same as the Speedparts, where as Abbott use a 40mm with a different internal air flow path. The Allard I have took just 3 hours to fit after Faero very kindly sent me some guidelines and I would say it was a 90% drop in replacement. I did advise Allard on moving the bottom mounting points and shortening the top pin so that the next 9K owner has even less trouble.
Anyway, I reccommend the Allard unit. It is one of the largest and still allows air/con to be retained. Oh, and it's the cheapest. Faero posted some pictures of his before installation if you do a search. My ECU isn't programmed to take advantage of it yet, but my car never seems to run out of power even at the rev limit.
Speedparts, Maptun(KylarJohnsson) and Abbott are the only non-'custom' ones on the market that I could find.
The 50mm Speedparts, Maptun and the Allard are pretty much identical in spec - none being better than the other.
Allard is very well made/sturdy but it needed a little thought when fitting and it took a while to arrive but was worth the £230+ saving imho.
I recommend Allard, but I'm biased as I got the ball rolling with a cheaper manufacturer. If you have money to spend give it to the specialists, if you want a similar or in my case a better product for less money go with Allard.
These are my personal thoughs only.
I see Abbott are reducing their prices...competition hotting up maybe...
faero - I think the Speedparts IC is Kylar Jonsson, I'm not sure who makes the MapTun one. I've used both, the 50 mm models. I'd say the MapTun is a tiny bit better than the Kylar Jonsson: the end tanks look like they'd be more efficient, flow-wise, and the overall finish, being polished, must add at least 5 hp Both were easy to install, however, the top pin had to be shortened on each, and they both their endtanks made the drivers' side (US) radiator support bulge-out, a bit. They make a noticeable difference in performance on a T5, even without software changes, but more so with the changes in programming.