What to Save Towards

My old computer still works. It is a Pentium 4, 1.4 Gigahertz, with 384 MB of RAM. I could probably go another year with it, but the monitor is fading like an old television. It no longer displays white, it displays bright grey. What I want is a new(ish) Apple because I think after the learning curve that I'll have to do less work to make it work. Trouble is no money right now. Well I have money I could pull out of savings and buy one right this minute, but that does not seem wise. And what if I want to work on things from work where we use Wintel boxes? So I am contemplating keeping this one going for another year or two by purchasing a new monitor. Nothing expensive, just a 20 inch LCD, that would set me back about $230 at Costco. But that could be about 15% of the purchase of a new Apple instead... What to do, what to do.