I'm saying its possible as this was the case for myself. My "advisor" told me its always better to attempt harder classes resulting in non-stellar grades than not to take harder classes and leave the adcom questioning your abilities. I guess if you don't get stellar grades in harder classes, the adcom will question your abilities anyway.
i think research is important. it shows adcom that you like a certain field, can produce output, and you know what research is about. not only does it look good to adcoms but also tests whether YOU like research or not. if you cannot find official RA positions, try taking seminar classes. seminar classes usually require papers that are supervised.
EDIT: GRE quant/analytical scores are important. gre quant is very basic; there is no reason why a phd student cannot perform well on it. I spoke with a member of adcom at UCI (where I am matriculating) about the admission process. they initially make GRE score cuts with math/stat/quant preparation following that. they want to know whether you can pass the core courses. from there they read sop, lors, and other items.