Advice on a new Macbook

Some background:

I have an early 2009 17" Macbook Pro that I use right now as my main computer. I keep CS5 on my laptop, and sometimes do some light work in Photoshop or InDesign, but that is very rare (photoshop is probably used once/month on this computer). I spend most of my time browsing, working in MS Office, listening to music, watching videos, and that's really about it. Also, I love OSX and agree with Josh about Windows being poison.

My MBP is starting to have a few issues. For one it is a little sluggish even after a fresh install of OSX a month ago, the body has taken a bit of a beating and worst of all the trackpad has some issues. I've replaced it once already and, though performance has improved it still has some issues.

The problem:

Anyways, I'm looking at upgrading to something new in the next year or so. I'm planning to go refurb if possible, as I'm on a a budget. I have about $1000 set aside now, and still am planning to save for some time before purchasing. I'd like to keep it under $2,000 if possible, so I have some time to decide. I'm really looking to get something lighter than what I have now, but I would also like it to be quick.

I'm tempted to go with a 13"MBA, but I think that would be a pretty drastic step down from the 17" screen. I've also been tempted by the 15" rMBP, but am nervous about not being able to upgrade the RAM. I'm curious, would getting a lower end, 8gb model suit my needs for quite a few years into the future(as I don't want to buy a new laptop after this one for sometime)? The cheapest 16gb models are in the $3000 range and that is just out of my price range. Also, I've heard these machines don't have that great of performance, which would frustrate me as I'm really looking for something that is quick. Finally, I also have the option of going with a standard 15" MBP, however these are heavy and I would really love to get something lighter.

I'm just curious if I could get some advice from people. Air owners, do you find that the machines are fast and adequate for the needs I mentioned? Is the 13" screen just too small? Also, can anyone answer my question about 8gb being adequate RAM for what I use my computer for?

Thanks in advance, any input is appreciated.