My 27" Imac has been a real pleasure to use. I program 80% of the time, and that much screen real estate can really help you keep everything you need for a certain development task visible at a glance. I have a larger 30" 2560x1600 screen on my linux box, and the more the merrier. It is worth it.
Also, I bought mine through apple's refurb program, and it's been running perfectly. I would suggest that as a good way to save some money.
Amen.... I've started to use more than one language, and it's made me a better programmer and far more understanding of how different languages approach problems.
PHP does have problems, but it's easy to pick up. I don't know that learning it will make you a better programmer, but a good programmer can definitely make it solve problems efficiently enough.