Adding sway bar rate at either end will cause the end with the bigger rate to slide first. So if you go too big out back, you car will be loose in the rear. Too big in the front and it will feel like it is not steering where you want.
If you have both factory bars, I would stick with them. The extra t-bar rate will help with the heavy front weight bias, the stock rear bar will help balance the inherent understeer. FWIW, the difference in rate between the stock .75 and an aftermarket 1.0 is only around 40# of force because of the significant difference in mounting points, assuming we are talking about the typical aftermarket axle hung unit. I have not had a chance to measure the layout and application of a Hotchkis bar yet, but since they are adjustable I'd say you can "tune" them to your liking. If your just driving on the street, you may or may not notice a big difference in the tuning range. There are lots of variables in driver ability when it comes to tuning.
