you can cut out some of the ulta low frequencies on the sylenth by setting a high pass eq at about 50 hz, that will make you able to pull up the volume a bit
you should set the overall volume somewhat down before you do that and at the end of your producing cycle turn the volume up with a limiter on the master volume
so it cannot clip, then you can do some tweaking, i dont know if you use dynamics on your master but it will make the track more dynamic like it says
it is not about volume of your mixdown, remember that, when i like a sound i just pump up the volume. Better make sure the sound of your mixdown is
ok en than at last put the volume of your mixdown up to a higher level,
if you want to listen if your mix has to much bass or to low bass you have to play it almost silently to hear if some things come more to the front, if you can hear the low bass then in your mix, there is to much in it, and if you cannot hear anything of the bass there it is set to low. Not on headphones btw.