Typically I recommend factory valves when available. But those can be both expensive and no longer available depending on the tractor.
Another thing to consider is the quality of the factory valves, they are not always top quality valves and have their own problems.
I don't believe that there are many if any 3rd party rear remote sets available that give you a 100% complete system. Most 3rd party systems are partial at best.
As far as the actual top & tilt cylinders, while there are several suppliers of the top links, the side links are few and much harder to find, especially that fit right.
You will most likely not go to a place such as Surplus Center and find the proper side link if you find one at all.
Even Kubota only offers the "T&T" sets for a few of their tractors and they have been out of those sets for the past couple of months and at last report will not have any available until February.
"T&T" sets will vary in cost depending on what tractor you have and what manufacturer that set is coming from.
Depending on the variables, a top & tilt set can run from around $800- over $2000. Again depending on what size machine they are going on, cat 1, 2, or even cat 3.
I hope that some of this information is of some help.