Living Room Legends Music Instruments

Anyways, the guitar is about a $250 squier, and I've invested another $150 installing a 3rd pickup, a special p-bass pick-up with a seperate output and volume control (too much detail to go into why I modded the guitar in this way). So I've invested about $400 in this guitar and I like my p-bass mod so if I bought another guitar I would want to do the same procedure.
My question is whether or not it is worth Improving this low-range guitar, am I going to be able to get high-quality tone if I install high quality pick-ups? Is there anything else I should replace? Am I going to be forever hampered by the fact that the neck is Bolt-on? I'm willing to spend plenty of money if it will make the guitar sound higher quality. Should I just bite the bullet, say the squier was a sunk cost and spend $1000+ on a high quality guitar? I'd like any advice you may have. Thanks!