Is it bad to use the remote wire from the deck to turn on two amps, a crossover and two fans?

yep.

use it to turn on a relay. The relay can run all that.

It should be okay, but ideally a relay would certainly increase reliability. Nothing worse than a burnt out remote circut.

Nope, I totally disagree. It won't be okay. With those 5 things on one remote line you will be drawing between 500mA - 1A. Too much current. If you do try it, hope your HU has overload protection so won't actually fry that portion of the head unit.

not gonna try it, my deck is an alpine 7894, and I don't want to frig it,

just use a relay, dont half a$$ it - there like $3 at princess auto

true.. for the price of a relay can you really loose?

ive been having a similar arguement on streetkiaz.com..... a guys amps overheating cus theres little to no airflow where its mounted, so i suggested a couple 2" fans on a switch in the dash, if he cant relocate the amp, someone said to just use the remote wire cus its easier, im like yea, and u run the risk of doin damage to your deck cus its not meant for that. took forever to convince them that its better to be safe, and run a separate line thats completely independant from anything else, then to have multiple things intertwined so when one thing goes it takes out everything else......

stupid people..... GRR

how much can you run off it before a relay would be advised? i just have two amps, and don't plan on adding anything except maybe more amps.

For myself, I would only run two things: ie two amps, or one amp and one crossover etc. You might be able to run three things, bu then you would be taxing that remote line a bit more. I go for safer than sorry. 2 - items for me.