Most people on here run progressives, me included. Your other option is race tech, imo may be better as they are set up for your weight rather than just being a one size fits all, I found them after I had already bought progressive springs. I may change mine out this winter just to try them and see what I like better. as far as install its not that bad really and a good time to change fluid, especially if you have a few miles on the bike. The downside is the tool you need for the left fork, its a castle nut type tool. some guys make theres, I bought one from kawasaki. this is the best price I have seen for one:
Kawasaki - 57001-1502 - FORK CYLINDER HOLDER
I have no problem lending mine out, but because of the expense of the tool I do require a $100 deposit and you pay shipping both ways (probably $6 each way), deposit will be returned when tool is back in my possession.
this is a write up on a vtx1800 fork spring change, it is pretty much identical to the mean streak, except maybe sizes of things:
Fork Spring Replacement (VTX 1800) « Bareass Choppers Motorcycle Tech Pages
Take a look thru it and see if it is something you would want to tackle yourself. I am not a mechanic by anymeans and have done it a few times on different bikes and as long as you take your time and pay attention to the order of parts its really not that hard to do.
I can take a pic of the tool later if you think you want to try and make one (I do not recommend making one, leaves to much chance of damaging the nut, or getting a metal shaving down in your fluid, I know this from trying to make one the first time I did it, now there are a lot of people with more fab skills than me that can probably make one just fine)