To return briefly to where we started, even in AMG guise the SL makes a superbly graceful cruiser, and one that seems inordinately classy. Sure, there'll be some cynical passers-by, but the SL evokes a more positive response from the general public than some of its obvious plush open-top GT rivals.
And AMG getting involved has done nothing to ruin said cruise. The 63's ride is a touch firmer than the 400's - as you'd hope and expect - but it's only the sharpest road-ruts that reveal the difference. Roof-down, which takes 18 seconds - and with highly recommended optional £525 wind deflector in place - the cabin remains brilliantly calm, even beyond 70mph.
But the 400 can do all of this. For your additional £40,000 you'd hope that AMG would added some magic. Happily, it has. Turning the rotary drive mode dial from Comfort through Sport to Sport+ firms the suspension, weights the steering, improves throttle response and alerts the gearbox, all in the name of enhanced performance and handling.
There's a brief pause while the V8's two turbos whine into life, before the SL 63 surges forward. Traction on, this is accompanied by a busy dash stability light. Traction off, and the 63's huge torque soon turns rubber to smoke. In both cases the standard sports exhaust spits furiously.
The 63 isn't all sledgehammer, though. While it doesn't offer the poise or outright agility of, say, a Ferrari California T HS, it does a very convincing job of changing direction given its near two-tonne kerb weight. There's a little autobahn vagueness around the straight ahead, but what lies beyond is precise and nicely weighted, if not particularly communicative.
Crucially, you feel involved in the process, although the ESP's halfway-house Sport setting could be a little less intrusive. Particularly given the 63's combination of long, lazy wheelbase, effective limited slip differential, responsive gearbox and accurate helm that help you build enough confidence to enjoy steering it on the throttle.
Two adults sit in complete comfort, even after the 63 swaps the 400's squishier pews for equally adjustable but more figure-hugging AMG seats. The steering wheel is also changed for an AMG sports example, while outside, our car's £2475 Night package turns its 19in alloy wheels, exhaust, mirror housings and other exterior details a moody black.