I'm not sure how loud you have to go to get the tubes cooking with the DT25 (good choice for an all-rounder amp by the way) as I haven't got one myself. But I did recently get an EVH 5150 III 50watt head & I was a bit concerned with getting the right tone at lower volumes, so I bought a Koch Dummyload attenuator.
Koch DummyLoad Home
This is one of the cheapest ones available at the minute (in Europe) & there's a slightly more expensive version that comes with a balanced XLR output. Before using this attenuator, I had to be very careful in setting the volume of my amp & could barely get the volume to 1. But with the dummyload set at medium 3% output, I can get the volume to about 3 (about 10 oclock) which is definitely enough to get the power tubes working. Another good thing about an attenuator like the Dummyload is that you can use it silently without a cab attached, feed the output directly to your audio interface & use cab only impulses (most impulses have the poweramp & cab sound) in your DAW.
I've only used Solid State/modelling amps & Amplitube until now, after finally owning a tube amp & recording it with a cheap mic, I can finally see what all the fuss is about. I A/b'd the EVH against Amplitube & there's just no camparison. The EVH amp recorded with a cheap vocal mic at a lower than ideal volume, sounds a lot better than Amplitube. No disrespect to IK or Amplitube, its a great & very convenient plugin. Its thanks to Amplitube & some of the newer amp models IK's come out with recently I got into proper tube amps, thinking
"if these amp models sound so good in Amplitube, how good would the real thing sound?" The EVH has answered that question......
Sorry for waffling on, but yeah a decent attenuator would do the trick. It can affect your tone at higher levels of attenuation, but low to mid levels of attenuation should be fine. Oh & always make sure the attenuator can take the wattage load of your amp. The Koch Dummyload is rated at 60watt which is just about enough for my EVH & should be more than enough for a DT25.