If you like the feel of your Squier, you may get enough improvement just by changing the pickups.
It's all good. I own a couple of Yamaha guitars, but I've also tried out few impressive Epiphones. The main thing is to 'try [u]before[/u] you buy'. So start prowling those shops, and spend some time checking out what's available.
Second-hand is a good way to get the best value for your dollars. I own 7 guitars, and only one of them was new when I bought it.
Use the search button at the top of the page to look through the posts that are already on this site. Read through the User Reviews at Harmony Central to find out what people who own a particular kind of guitar think of it.
Happy hunting! :)