Just for a small amount of Devil's Advocacy, before you go too much further, 1920x1200 displays of reasonable quality are always coming down in price:
http://www.newegg.com/Product/Product.aspx?Item=N82E16824176346
Have you looked at completed eBay listings or the like to see if people are even willing to pay >$300 for the previous generation of Cinema display? I just ask because at $100 over $285, you're in UltraSharp 2412m territory, and that's an exceedingly good and flexible display. (Dell has one today for $390, with a three year warranty and the sound bar, which tends to be good for desktop audio.)
Re the Mac Pro: I haven't looked in the last few days, but a few weeks/months ago, the concensus was that Apple was going to wait until either later in the year or next year for Xeons using the Haswell or Ivy Bridge microarch. As it stands, today's current generation "big" Xeons (anything that can run in a dual socket system) are based vaguely on Sandy Bridge and the xeons the Mac Pro is using are only one generation prior to that. Some of the smallest Xeons are essentially the same as the Ivy Bridge i7 chips, but Apple is totally unlikely to release a machine based on one of those Xeons, because that would put it in the same class as Dell systems like the Precision 1650 or the OptiPlex 7010/9010, which is essentially the "Mythical Midrange Mac Minitower" which will never exist.
I don't know (read: haven't looked up) whether Intel is going to be skipping the Ivy Bridge microarch on it's bigger Xeons in favor of Haswell, or if they're going to be shipping the SB-E Xeons out until the thing after Haswell shows up. As it stands, in terms of compute horsepower, Ivy Bridge isn't that big an improvement on Sandy Bridge, and I've heard Haswell isn't going to be particularly exciting on the desktop, other than that IVB has marked the end of Intel building its own standalone system boards.
So, if you want a Mac Pro, and you can afford it and it'll be faster than what you're currently using (which would essentially demand you buy the eight or twelve-core system if you're currently using an i7-3770) and it'll make you money, I'd say now is as good a time as any to buy one. If you'll lose money if you don't have the system, then by all means pick one up today in order to capture that profit opportunity.
If you don't need a Mac Pro immediately, or you want a fast Mac but don't want ot put money into a Mac Pro that'll be replaced by something two or three computing generations newer in the next year or so, then you may consider getting an iMac or one of the quad-core Mac minis. I suppose it depends a lot on your workload and whether or not adding things like really big GPUs (GTX680 became available for Mac recently), >32 gigs of ram, four disks or other Mac Pro specific things will be of more benefit than having an exceedingly fast single-socket system.
On the other other hand, if you're getting your work done with what you've already got handy, then you may consider stashing that money for a rainy day or a big emergency, which seems to come up on a regular basis. It's commonly said that ideally, you want to have two months of the salary you'd need to live and support yourself on hand in the case of a medical emergency, a sudden loss of job, or other things. (Having two months of living expenses on hand helps tremendously too if you need to move and pay to rent a truck and then pay two months rent up front, as another example.)
Good luck with the monitor, keep us posted on what you end up doing with it.