Mercedes SLK 55 AMG
Why 6.8: A hand-built M113 V8 in a small folding-hardtop roadster, sold new for barely more than a loaded SLK350. Cheap enough used that it gets bought by people who actually want to drive an AMG V8, not just own the badge.
Layout
Natural habitat
Ride comfort
Sound
The 5.4 M113 gives the deep, lazy naturally aspirated burble AMG built its reputation on, and it rasps properly past 4,000 rpm. But this is the soft-tuned roadster version with heavy silencing and no real top end, so it woofles where the later 6.2 cars roar.
8-cylinder · naturally aspirated · 7,000 rpm redline · rated 7.1 / 10 for engine sound
Market value
Median asking price, good condition · €56k (2005) → €26k (2026), trending down · illustrative data
Child seats · ISOFIX
There aren't any — strict two-seater.
No ISOFIX anchors on the front passenger seat. Mercedes fits the AKSE transponder system instead — an approved Mercedes child seat, secured by the seatbelt, is recognized automatically and the airbag switches off.
The R171 has no rear seats at all, so AKSE up front is the only factory-sanctioned way to carry a child.
R171 SLK owner-forum consensus (SLKWorld, MBWorld) on ISOFIX/AKSE fitment (owner-community sourced, not manufacturer documentation)
The long version
The SLK55 undercut every other V8 AMG on price when new, which meant it drew buyers who wanted the drivetrain rather than the flagship status, a formula that still holds in the used market today. It never got the extremes that make the later Black Series version a trophy car: no fixed roof, no track aero, just a torquey naturally aspirated V8 in a comfortable folding-hardtop roadster that a lot of owners genuinely use for weekend and commuting duty. Depreciation has been brutal and long since bottomed out, which is exactly the used-Boxster-adjacent price window that keeps these driven instead of stored. It is the unglamorous, honest sibling to the Black Series parked two rows over at any AMG meet, less special on paper, more likely to have real miles on the odometer.