I've installed cartridge emulators and correctly rated straight rate springs on three of my bikes over the years--XS650D, Suzuki SV650, and Suzuki GS500E. I always use Race-Tech emulators, for two reasons. The first is ethical. Paul Thede of Race Tech invented the emulator valves, and I feel that buying pirated copies is collaborating in theft. Second, there's a spring in the valve that controls its action, and the rate of that spring must be correct for the valve to function effectively. I don't trust Chinese makers to produce the spring to correct or consistent standards; they tend to work on the principle that if it looks good enough, it is good enough.
As to stiffness: the emulator valves enable damping to respond to the road surface, and the result is that when stiffer springs are used (and they should be!) ride comfort is not lost but improved, and compliance is much improved.
As to shocks: steering becomes much quicker and more linear on the XS650 when the rear is lifted. I recommend eye-to-eye free length of 13.25" to 13.75" for Standard models, 13.5" to 14" for Specials. I use 13.25" custom alloy body shocks from Works Performance that were made to my specifications with the fork tubes raised 1/2" in the clamps. The shocks were around $550 for the pair when I bought them in 2003 and they'd be a lot more now. YSS makes some nice twin shocks with responsive damping; Google for the URL. They're made to order in Thailand, so you'll wait a few weeks for delivery. The Thais are getting a very good reputation for quality aftermarket bits, and it's well deserved; I hung a YSS monoshock on my little 500 Zook, and I'm very pleased with it. The higher end Hagon shock--the one with adjustable damping--looks like good bang for the buck.
Before you spend a bunch of money, read everything you can get your hands on re. suspension tuning procedures, and if you hop up your suspension, get yourself some better tires! I liked Avon Venoms, but those "universal" tires you're using don't have carcasses designed for the differences in load applied to the front and rear wheels of a motorcycle; they're strictly utility stuff.
I've written all of this up before, and I suggest you look up previous discussions and get other views as well. Just be aware of Paul Thede's maxim: "The best you've ridden is the best you know."