Nice budget... You have a lot of options. Botht eh Spyder and yeti are very good. For that money, I would also look at a Titus Racer-X (probably you could go titanium and custom sized), Ventana El Saltamontes, Turner Flux, Ellsworth probably has some good options too, but I don't know much about that line.
It's not only about geometry, but I'm finding that having two bikes similar geometry, but one is a FS and the other a HT, because of sag, when you're riding they will feel different.
Also, try to get a adjustable travel fork (right now, most companies offer different options for this), this will help you also on climbs since you can lower the front of the bike on climbs, and raise it for flats and descends.
Also, pay attention to the wheelsets, since not only weight saving is important, the hub is also very much so. Depending on how you build the bike, you can go for Industry-9 hubs, or Chris King, or Hadley rear hub with 79 or more engagement points. Current Shimano (except for 07 XTR), mavic and most standard hubs have 18 engagement points, or close to it. Hope has 24 on the Pro II hub, or 36 on the Bulb. This makes differences when you're climbing, or have to restart a climb at the middle of it.
I don't think you'll get a 19 lbs reachable target, but probably somewhere around 23-25 lbs. But I might be wrong on this. On weight, put attention on tires that are light and have low rolling resistance, and rims too.