The two options that I tried were the generic Truglo big fat front sight. It drew my eye TO the front sight as intended BUT I was never satisfied with the rear sights. No amount of attention could get them to stay locked place.
The only full aftermarket sight system for the 709 at the time (and STILL - others chime in if I'm wrong) are the somewhat unconventional appearing Advantage Tactical 'stacking pyramid' sight system.
The rear is well engineered and is windage adjustable. The front is well made and is elevation adjustable using a system of included shims. The color combinations front and rear are extensive and easy to swap. The company has been around for a while in a few forms - this is their most successful product to date.
CS is great, they are a little pricey BUT many folks are using them AND the owner of the company has a 709 and offered me personal advise on an initial setup to try - still using that today!
I shoot very well with them. The learning curve was minimal to none for me - YMMV.
The website pics are better than shots of my gun to illustrate the design and function of the sight system.
........This is the sight picture with some color variations.
*the company has begun talks to supply the entire Taurus lineup in the future!