i'd wait till the price went down some. good monitors are dirt cheap right now. if you need one, i'd definitely choose that over a new SSD. you can probably get an awesome monitor for what you will pay for a 120gb SSD.
*edit* looked at your link...i dont get you redcoats' money system pounds and pence and shillings and all that, but the ocz solid is 185 pounds which is *trusty internet currency converter* thats 275 bucks and you can DEFINITELY get a good 24" monitor for that much.