Togu-audio-line makes some pritty dope synths like TAL-NoiseMaker and TAL-Bassline 101.
Other than that U-He has a few decent free plugins. The best of them I find Tyrell n6.
Other than that I could advise using some distortion on your bassline which brings out the low mids to get the KHSMR kinda bass you are looking for
Superior Drummer 2 w. Metal Foundry SDX expansion
Guitar and Bass
Shreddage 2 - The shreddage plugins are at the moment the only decent solutions (IMO):
Take a look at this summary for other alternatives.
There are soo many. I'd invest my time in something ...