If you did use a DI in addition to the blonde, where would you put the DI in your signal chain?
I'm pretty sure that, for this application with a PA, a DI would be best placed last in line, right before the PA's mixer input.
Otherwise, placing it in-between any other NON balanced devices, you'd completely lose the benefits of the DI.
Note that the Blonde DOES have a speaker-sim; it has its own, on-board "Jensen"-colored speaker-simulation that is always on- it can't be turned off or bypassed, AFAIK.
And, you could easily use the Blonde WITHOUT a DI, that's essentially what it's for- you would just have to be careful when setting its controls. It's a SansAmp that's been tweaked and optimized to favor vintage Fender flavors. But having a balanced output via a quality DI interface wouldn't be a bad idea.