Well the question is how did you find bass of Solos? Sure the Solos are muddy but that's because the frequency response looks like a steep downhill.
LP2 have a little less bass than Solos, M80 quite a bit less (quite gently boosted bass). M80 are definitely better sounding if you can accept the less bass quantity which isn't always a given for a basshead. Ofc there's other options than LP2 if heavy bass response is important, LP2 isn't the very best in terms of price/sound quality, I personally that has tested at least quite a few headphones found them underperforming for their asking price while the general concensus of M80 is to be very good sounding at the price point. Still having said that LP2 comes like a "natural" upgrade to Solo headphones as they have similar sound signatures the LP2 just less extreme so for better balance. The Solos have VERY recessed/lacking/non-existant high frequencies while the LP2 just have "recessed/lacking" high frequencies and the bass is slightly less strong in LP2 but also better quality.