How much are they? If just a steel plate with holes drilled in at the correct position....heck....you can do that yourself if you so choose.....
The ones that screw or use threaded rods so to speak are a bit of an overkill imho. Expensive too from what I recall....? There are kits out there that lower the bike a certain amount for a reason......there is only so far you can go before you will bottom out something and things will connect. Personally I would buy the solid version at the hieght you desire and try them over adjustable ones....but it's your machine....so you need to decide.
I bet you will soon get used to the stock hieght and eventually put it back there, from what others have reported.
Also, how heavy are you? This will also dictate what spring rate you need to be using when you think about stiffening the suspension down the road. The bike was designed for a 165lb rider with 30lbs of luggage....most of us just sitting on the bike naked would overpower that limit, so a heavier spring is needed. You can just respring your stock shock with great success, I have and many others as well. It is a cheaper way to get the bike back to a designed working suspension. I'm 205 soaking wet and use a 7.4kg spring from TopGun...love it. It allows me to still use the stock shock and all it's settings and also carry all my camping equipment when I go on my adventures.
If you are a tad bit heavier than the 165lb range, you already are lowering your bike with that weight and overpowering your stock spring which will over work the shock and cause it to prematurely fail. Just saying.
There is a few things to concider when talking suspension levels.....not just linkages.....I'm sorry to say.....
The Soupy's are $103 everywhere I looked. What I like is the adjustment capability as well as their being made of steel. If I set it 1½" lower and later decide 1" or 2" - or 0" - might be better, they'd give me that option without buying a new set for $70 or $80 and tearing the whole thing apart again.
As I've said in other threads, I'm not even a little bit interested in jumping logs and roaring down rocky trails, nor am I interested in howling around 30 mph curves at 70 mph or doing wheelies. I'm pretty old now and more conservative and I want the security of a little more range with my feet.
(one benefit of doing this is that with it dis-assembled that far I can also check the lubricant in the swing arms, etc., etc.)
I weigh about 185, fully dressed with my boots on and "always" carry about 10 - 15 # of camera equipment. I'm a paranoid so always carry basic tools and tire kit - a few sockets, etc. I live in a semi-arid area and always carry an extra day's water and a few energy bars, JIC.
I've looked at the Top Gun site and today will be ordering the 6.6 kg spring unless they recommend otherwise. As I've said earlier, I've done a huge amount of reading on all this, but it's hard to assimilate all at once. Getting help from people like yourself can save a lot of fussing and experimenting.
Since there are so many opinions about almost everything out there, I try to listen to each person's input, then make a decision. "Usually" works out pretty good. In things I'm familiar with, I'm always happy to help out beginners in those - and I do that in story format with lots of pictures.