I don't think you're going to find any (or at least many) modern video cards with YPbPr out. AMD/ATI cards are pretty much only DVI, HDMI, and DisplayPort, with D-SUB on the lower-end cards. nVidia is the same, except no DisplayPort. Your best bet is probably a converter, if you really need YPbPr.
Unless you plan to game on both monitors at once (completely possible), you don't need a very high-end video card. If you're considering upgrading to a 1920x1080 monitor or two in the near future, then it might be worthwhile to get a bigger video card now, though.
Intel is coming out with the new processor line Sandy Bridge in about the first week of January. It's likely that a build using that processor will come in near the high end of your budget, if not above it, so the best reason to wait for it is to see what effect it has on the pricing of other chips. At any rate, an AMD Phenom II X4 is more than enough for gaming and standard office work. If you chose to upgrade to an i5 or Sandy Bridge build, all you would need to change from the build below is the processor & mobo.
Note that I didn't look for combos, just lowest individual components, to give you an idea of what to look for. There are definitely some good deals out there that will bring the cost down a little.
AMD build:
CPU -
AMD Phenom II X4 955 - $145
Mobo -
Gigabyte 870A-UD3 - $95 - USB 3.0 & SATA 6.0 Gb/s
RAM -
Geil 4 GB kit - $49 + $1 shipping - not amazing specs, but decent
GPU -
MSI 5770 1 GB - $140
or go with a
6850 for a little more future-resistance
SSD -
Corsair Force 60 GB - $126 (-$20 MIR)
HDD -
Samsung Spinpoint F3 1 TB - $55 - currently on sale for the 500 GB price!!!
PSU -
Antec EarthWatts 650W - $70 - possibly slight overkill, but a very good PSU
Case -
Antec 300 Illusion - $70 + free shipping
OS -
Win 7 Home Premium 64-bit OEM - $100
Total: $845 with the 5770
You could go with a slightly smaller PSU to save a little money, or potentially shave off $50 or so with combos. Alternatively, go with a 6850 or similar $200ish video card (GTX 460 1 GB, AMD 6870, GTX 470) for the future and keep the EarthWatts if you want to spend a little more.