RE: X51-R2 Upgrade
Well yes, you can upgrade the PSU. Just get the 330w PSU and you'll be good to go with a GTX 970.
With a 240w PSU, the best you can get is a GTX 750 ti.
Currently owned computers:
AW13 R2 | i7-6500U | GTX 960m 4 GB + GA (R9 285 2 GB / RX 480 8 GB) | 16 GB 1600 MHz | 1800p Touchscreen | 2 x 500 GB SATA M.2 | Graphics Amplifier Performance Analysis with 13 R1
Desktop | i7-3770 | GTX 980 4 GB | 16 GB 1600 MHz | 120 GB mSATA + 960 GB SSD + 2 TB HDD | 600w PSU
Formerly owned computers:
HP Pavilion 15-n280us (given away) | Apple Mac Mini 2012 (sold) | m15x (damaged mobo) | 13 R1 (death by unknown) | m14xR2 (Tradied In)