I feel your pain on the price. I'm going to wait until tax time as well. I know that I will be going with a 9" because I don't want to hear the 12 bolt gear noise. I just don't know what center section option to go with.
I'm not sure if you saw it, but in another thread on ls1tech, a sponsor had this to say:
The more splines, the stronger the axle. 35 spline axles will handle just about anything you're going to send their way.
A spool locks both axles together, all the time. It is the cheapest way to go, and is the strongest, but for a lot of street drivers they would not find a spool to be tolerable. Why? Think of what your tires do when you turn a corner, the outer tire needs to turn more revolutions than the inner tire. If it can't, they squirm and are forced to turn whether they want to or not. Usually this just results in accelerated tire wear. Most of my driving is rural and highway, so I can drive a car with a spool and hardly ever notice it.
I use to highly recommend the Eaton (use to be Detroit) Truetrac for up to 600 rwhp, but lately I have been having customers with some problems with them. I'm not sure if Eaton made some changes for the worse when they bought them out, but I never had any problems with the Truetrac until this year. They still have a good track record, but I wouldn't recommend one if you're going to spray nitrous. The Truetrac can only be had with 28 or 31 spline axles.
The locker is a very strong unit that can handle a lot of power. It isn't much more than a Truetrac and can be had with 35 spline axles. It does have some negatives to it though. The locker can cause the back of the car to wiggle around when you let off the gas, as it doesn't always unlock each axle at the same time. It doesn't happen with every car, but I've driven one that did. I remember that I got out of the car and made sure the rear was still bolted in, it felt that strange. If you get a good one if will do everything you want it to.
The Wavetrac is relatively new and is more ($460 more) expensive, but it comes with a limited lifetime warranty. 35 spline axles can be had with it, and so far I haven't hear anything bad about it.