Welcome
There are a few suspension threads, this one has a table of shocks from other bikes with lengths etc:
https://forums.sv650.org/showthread.php?t=139058
This next one is for insomniacs since it goes on for 51 pages:
https://forums.sv650.org/showthread.php?t=137793
I haven't read it so I don't what they talked about for so many pages.
I recently bought a new shock for my Yam - Nitron, K-Tech, Maxton, M-shock, YSS all seem to be roughly in the £450-£550 range, more if you want a remote reservoir. The German shock (Wilbers) was more expensive for us in the UK. The advantage with buying new is that they will fit a spring according to your weight, disadvantage is price.
Brakes - the SV is known for having weak brakes - harder pads, braided lines all help. Some have changed the front end (forks from a GSXR) which gives better front suspension and brakes - "Bibio" is an excellent source of info on that.