I've noticed something funny with boss me80. If I use the high gain amp model labelled 'metal' into my dsl - initially it sounds a bit compressed and unnatural. However, after playing along to some cds for an hour or two it sounded freaking amazing - the subtleties were all there and I doubt I could get better. It was plugged directly into the input channel of the dsl 40 watt combo with volume on 2.
So is this -
a) just my ears getting accustomed to the sound
b) the dsl tubes getting warmed and reacting differently to the sound.

Honestly, your ears are probably fatigued. To verify, record yourself playing the same thing a few minutes after the amp warms up, and an hour or two later. Keep settings/mic placement the same, and play the same thing. Compare the two recordings on another day (or later) when your ears have had some rest.
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Michael Kelly Patriot Glory
Ibanez RG8
Blackstar HT 20 w/ Jet City cab
whole bunch o' pedals