Personal experience with that level of gear tells me you'll be fine. They'll serve. While a swankier DI solution is probably better in terms of getting bigger bottom or clearer top end, you're blasting this through a guitar amp with, presumably, a mountain of gain. You'll live. My small crew of noisemakers I work with do this regularly. Unless you are playing the amp, as it were, as part of your sound, there shouldn't be much issue. For fairly undynamic rock riffs, you should be good.
I will go out on a limb regarding their past experiences with reamping self-produced tracks. I am going to guess "poorly recorded"- levels either very hot or very low (probably the former), noisy, shoddy playing, etc. I treat DI tracks the same way I do anything else, and try to keep peaks around -12dB or so on the way in. This means your average level will be pretty low. Basic digital gain staging stuff. With modern 24 bit digital, you want headroom. You don't want to be slamming things into the red. Watch/listen for noise from pickups near computer monitors. Etc. Unfortunately, the onus is on you guys not to bugger up the recording. Getting it to a guitar amp is the easy part. Probably.
Honestly, if your studio peeps are making a big deal out of it, I'm tempted to say we can give it a shot here through whatever we've got kicking about at the moment, if Diezels and Mesas and vintage Marshall cabs, Warm Audio preamps, Audient converters and the like are acceptably not crap...
