Your original strike water temperature is calculated so that it is at the proper temperature to allow you mash to settle at water ever your mash temperature is. For example, you might have to have your strike water at about 163F, so that when it is combined with your grains, you settle at 154F (your mash temp). You mash temp can be anywhere from 148F to 156F, depending on the recipe.
I heat that .89 gallon sparge to boiling and stir it in. That has never brought my mash up to the mash out temperature of 168F. When you look at the mash schedule and see that it says to sparge with .89 gallons and 3.5 gallons at 168F, that doesn't mean that you want the sparge water at 168F before stirring in into the mash. It means that you want the mash (grains + original strike water + sparge water) at 168F, after stirring the sparge water into the mash.
When I've added the small sparge addition to the mash (grains and original strike water), I've never had it come up to 168F. You just can't get it hot enough, unless you're able to add heat directly to your mash tun. I use 48 quart coolers for mash tuns, so I can't just turn the burner on and bring it up to 168F. I have to drain some wort out of the mash tun and heat it in my boil pot, then return it to the mash.
You can use the "decoction volume" tool in BeerSmith to get a good idea of how much wort to pull out and what temperature to raise it to before adding it back into your mash.