Macbook Pro for full time video editor?

So i have the either 2010 or 2011 iMac for video editing. It is starting to run slow but instead of upgrading it i am thinking of getting a macbook pro since I need a laptop anyway. Is the $1500 macbook 13.3 inch i7 worth the price, or would I find a faster editing machine somewhere else? I will be using my current imac for just web use and my macbook for just editing. Is there a cheap 24inch or bigger monitor I should get with it for using at home? Is there somewhere better to buy, or would I be better of going with a used 15inch macbook pro off ebay? I'm just not sure how great this computer will be for video editing at such a high price. Any suggestions or help would be great. Also wondering if there will be a new line of macbooks coming out soon I should wait for?