right now i have 2 of the big 17 that i play on.. would it be worth the money to have the 19s? or are my winnings just burning a hole in my pocket?

i want to be able to 8 table

I'm not an expert but here goes. Its easy if you have a video card in your computer that has a DVI out port. There is a DVI to VGA connector ( about $25) that you can use to to hook up a regular moniter to the DVI port. You then also have a moniter on the normal VGA port of the video card. Hook the moniters up, then right click the desktop to bring up the video settings and it should automatically find the second moniter. Its probably best to make settings "extend desktop" but play around with it to find the best setting. If you dont have a video card with DVI out it can be harder. You can set up a second video card (PCI) along with your original, but I have never had much luck with this working out. Easiest by far is to get a video card that has either a DVI port or a card with 2 vga out ports. There are a lot of websites that can help you walk through the process to set up dual moniters or to install a new vid card.
Hope this helps.

One aspect of buying a new monitor/monitors that I have yet to see addressed here is monitor quality. If you are someone that plays at least a couple hours per day on average, I would STRONGLY suggest you (and this goes to anyone) buy the highest quality monitor that you can get in the price range you can afford, even if this means getting a smaller monitor instead of a cheaper big monitor. Why you ask? Eye strain.

Typically lower quality monitors can only display the highest resolutions (the ones you would use for 4-tabling with no overlap for instance) at lower frequency, resulting in a slight image flicker (somtimes noticable, sometimes not quite noticeable), which under prolonged use can cause eye strain which in turn can lead to headaches or other symptoms of stress. Higher quality monitors will not show this flicker at the highest resolutions, thus greatly reducing any potential for eye strain. Typically you want your monitor to display your preferred resolution at a frequency of at least 72 Hz (meaning it updates the image 72 times per second). This is true for any CRT-type monitor.

If you are looking at LCD monitors instead, the display frequency is largely irrelevant because of the way they work (most that I've come across display at 60 Hz which is more than adequate for this type of display). Instead, you should be looking at contrast ratio (measures difference in light intensity from bright white and dark black -- something 500:1 or higher is pretty good), brightness (to be honest I'm not quite sure what a good baseline amount would be, but brighter is better), and response time (this is a measure of how quickly the monitor responds to an image change -- 20-25ms is adequate if all you do is play poker and web-surf, but for gamers or if you watch movies on your PC you want at least 15ms response time, preferrable lower).

As a part-time computer science student, long time PC gamer, and someone who plays on average 30-35 hours per week of poker, I spend an awful lot of time in front of the computer (and yes, I do get outside from time to time too, so shut yer mouth...) and I can tell you that the long term difference that monitor quality can make is amazing. Since we are all here to improve our game in any/every way possible it seems pretty obvious to me that the more comfortable you can make your computer time, the better your focus will be and in turn you will get more enjoyment (and hopefully more $$$) in the long run.

Hope that is helpful.