Help finding a movie where a wife kills husband's mistress with a power saw

I need help finding a movie from 2000s (maybe late 90s). I saw this movie when I was ~11 (18 now) so I don’t remember much of the plot and I haven’t finished the film because one scene that traumatized me and made me turn it off. From what I recall the plot was about a man cheating on his wife and having a LOT of sex on screen. One day his wife finds out about this and tells him to bring her to their house. The next day he drugs her and stuffs her into his car trunk, he then drives home to his garage where his wife waits. She tells the man to put the girl on a table where she proceeds to chop her up with a power saw ( I have no idea how graphic that scene was because I closed my eyes when that was happening). I then forced myself to watch a bit more of the movie. The last scene I remember is when the husband goes to a bar and talks with some other men, he then walks out and puts on his sunglasses while a song starts playing.