Nah man, I've done plenty of 'real psyches' and though dxm isn't my favourite drug it's definitely worth exploring. Disassociative drugs are their own thing and the experience doesn't really relate to psychedelia.
If you can get it, ket is obviously the better choice, but if you can't dxm is perfectly fine. Though, if you're drinking cough medecine you will get sick, period, expect it and just roll with it. The great thing about disassociatives is that even if you are feeling sick...you don't really care all that much.
In any event, if you really want to 'trip' on dxm you're dosage is going to need a hell of a lot more than 177mg, like more than double. (Though if by that you meant 177mL, do the math on what the syrup is mg/mL wise and go from there...though 177mL will still probably not be enough.) And don't drink the shit with guaifensin, that will make you sick on a whole new level.