SP101 upgrade bits...
Lots of people swear by Wolff springs.
I like the factory grips myself, but the Hogues have a good rep too and the rubber Hogues aren't very expensive. If the factory grip feels "wrong", by all means experiment, grips are very personal.
I prefer the Ashley Outdoors Small Dot Tritium front sight over the Trijicon. The Ashley is available, although it's not in their HTML online catalog last time I looked. It IS in the bog downloadable catalog, or call them...website is
www.ashleyoutdoors.com
Ashley uses a Tritium tube just like a Trijicon, but surrounds it with a white enamel dot. In daylight, the Ashley is worlds ahead.
With any replacement front sight, you may need to paint the rear sight. I'd consider painting the entire rear outline orange, but that's something I'd want to experiment with. Possibly red instead of orange. You want the white dot with tritium inner dot to be the brightest.
What else...if brand-new factory ammo of good quality is "tight" within each cylinder bore, you might consider getting a Brownell's cylinder hone kit for .357cal. Used very moderately, mirror-polishing the cylinder bores will make them easier to clean and will let the empties drop out faster. This is a quick home gunsmith mod. If the cylinder bores already allow the shells to "slop around a bit", consider avoiding this and whatever you do, go real easy and follow directions.
You need speedloaders. I loaned a friend who owns an SP101 one of my HKS twist-release types from my J-class snubbie; first point is that SP101s eat from standard S&W J-Frame .38/.357 speedloaders. Second nice surprise is that the HKS at least cleared the rubber on the factory grips just fine. Nice going, Ruger!
Speedloaders that are "push-button release" are faster...Safariland makes these, and others. I don't think the body bore on these is greater than the HKS types, so they should clear the factory rubber just fine as well. Brownells and Dillon sell speedloaders, among others.
This is a good start.