Going from top to bottom: I really like the first one, the next two I won't be able to tell without hearing more of the song, and the last one sounds angry in a good way.
Note: Only one speaker was knocked over, but it was done intentionally (I'm trying to fit in).
I really liked the samples. Will the mastering take away the rumbling bass frequences and compress loud stuff while boosting quiet bits? If so, don't do it!
I guessed something like that, but isn't compression part of mixing? Oh wait, I guess compressing idividual patterns, tracks and voices would be compression on the mixing level, and the overal compression/shelving/equalizing of a song would be mastering?
If so, the guys that say 'fix it in the mastering' are jerks.