Actually, the engine in the last video is a 5.5l Twin Turbo V12 (M275). It makes 493HP stock in the S600 (W220) which can be found for around $11K. It sounds great to me!
The M120 is a 6.0L V12 that makes 389HP stock. This engine is found in the '91 - '98 600SEL, 600SELC, CL600 (W140) and the '92 - '01 600SL & SL600 (R129). These cars can be had in the $7K - $9K range.
Love the discussion. Let's keep it going!