ok, whenever I take corner and mistakenly downshift to...oh lets say 3rd gear @ about 25mph, when im supposed to rev-match and shift to 2nd, my engine starts to rattle.

I know it does that a little bit in all MT (at least G's), in trying to accelerate at such high gear in low speed, but my car rattles rather very loud.

Also, when im constantly crawling/stopping on the highway during rush hour, when I go from neutral @about 7 mph rolling, to 2nd gear, the engine bay rattles. it feels alot like the rattling and the noise is comming from the tranny, and not the engine.
It also rattles during above condition, from full stop neutral to 1st gear.

is my car due for new clutch? I know I burned my clutch like biatch since this was my first MT. 50k mile on the car now.

 

Are the motor mounts in good shape? That's where I'd check.

 

Usually all the bad clutches i have seen just let the car rev like crazy but never have shaken. I suppose it could be your clutch or could be bad syncros which would be a worst case. I would definitely look at your motor mounts first but also check your exhaust if a hanger is broken it could rattle at certain frequencies and cause a lot of noise. Since it passes by your transmission it could be the case