Macbook Pro and Air worth fixing or should i replace?

[jchris28]

Ok so simply i have 2 Macbooks and was wondering if i can upgrade one of them for good prices instead of buying a new one. I produce music, edit videos and edit photos so i do need a computer that can handle a lot of activity at once and still give me very smooth and powerful responses. I current have a Mid 2009 Macbook Pro 15inch with 4GB of ram something around a 2.3gHz Core2Duo (gHz off the top of my head) and its old 500GB HD. Then i have my... 2011 or 2012 Macbook Air 11inch with 4GB of ram and a 1.6gHz i5 with its stock hard drive. Now i was scheming on a new 13inch Pro non-retina (to save money) strapped with an i7 2.9gHz with a 3.6gHz boost and an 8GB of ram. Currently i was thinking my Air because its newer and has a better processor. Also my battery has deteriorated so bad that when it gets unplugged it turns off so that needs to be replaced as well. Now when i turn my computer on its SUPER laggy and heats up really quick but i figure that stems from my battery problem. I was wondering, if i strap say a Samsung 850 Pro SSD to either of my laptops and up the ram to 8+GB, and replace the battery if its my air, if i could get a powerful performance able enough to handle what i do. Appreciate any input, thank you!