Two rings or One ring?

If you need to ask...you probably don't need a double. It all depends on what you encounter on your rides. I regularly have to climb steep fireroads on my AM/mini-dh bike, so a granny gear is mandatory.

I switched from a dual ring setup to single this year and love it. Way smoother, less wear, less weight, etc. I'll never go back to dual ring for DH, but getting the perfect gearing can be a challenge too.

I'd run a 34t ring with an 11-34 in the back. That's what I usually run and it works well for me, even with some steep climbs. The only time I'd like to get into a lower gear, it's usually faster to walk anyway.

That said, if you like to ride technical uphill singletrack, a granny might make a big difference.

Unless your planning on also using it for some longer climbs, then go with a single... Most of what youi listed for what you want to use it will have no need for a granny ring, and youlll still have plenty to get up and pedal when you need a bit as it is.

I think either a 36 or a 34 in the front, with a 34 or 32 for a low range inthe rear will bhe just fine

Another vote for single. That's what I have on my do it all hardtail.

Since you already have the cranks/guide for it, try it out for a while and see if you still think you need a granny.

I roll with 36 / 11-34 for do it all play bike. But I walk most climbs. What fun is it to spin along at walking speeds? I say go for a 1x9 setup.

My $.02

I have always HATED front derailleurs, so all of my bikes have been setup with a single ring, varried in size from a 32 on the 5" bike, to a 38 on the dh bike.

I recently picked up a 2010 Enduro and have come to LOVE front derailleurs (if setup properly). I'm running the new SLX FD designed for 2x9 with an x9 shifter. Love the system, its so nice to be able to drop to the granny for steeper sections of climbs, or long climbs in general. The bike also came with a command post which I love as well, pop it up for climbing sections, drop down to rip the singletrack.

My suggestion is that if you are going to be doing any serious climbing, opt for the double. At least around here we have ~3000 feet of vertical just minutes from downtown. I couldn't imagine spinning for 2 hours without the granny.

EDIT: If you plan on doing any racing with it, its pretty easy to just remove the FD and throw on a different chainring. Its what I will do with my Enduro if I end up racing any courses that dont require the DH bike. I've got a spare chainguide, single ring and a short seatpost to save the weight.

I have a similar bike to the one you are building at I am running a single ring 34t with a 11-34 out back. The bike is more oriented to the gravity side of things but it climbs pretty well. On my more pedally hardtail I am running a dual ring with a blackspire stinger guide. I just changed the gearing to 36/22 with an 11-28 cassette. The 22 is still a bit small so I may go 24 or even 38/26, but I have also been thinking about going to a single ring setup on this bike too. I guess what I am trying to say is if I were you I would choose single ring. Also, this may not be applicable to your chainguide/frame but on my do-it-all rig I too have the slx cranks, and with the e13 LS1 guide it is hard to get it spaced correctly due to the granny tabs. I ended up grinding mine off...

Your lowest theoretical gear with 1 front chainring will be about 1:1. If the trail is so steep that you can't make it up with that it would be faster to walk.