First make sure you can't solve your problem by moving to a more powerful server. 145GB is tiny. 256GB of DDR3 is less than $600 on eBay, and can fit your whole DB.
Also, are you on a SSD?
Also, are you on a SSD?
Have you looked into why your slow queries are slow? Seems like indexes are missing, or your queries are unoptimized.
Please share pointers, if any.
Wow - I see PC builders paying $150+ for 16GB. I guess ram really goes down in price once you start buying in bulk / server memory.