How long is a piece of string? If it is just for a set of speakers, and you have no plans for anything bigger, 8 guage is probably ok. If you plan yo go to subs, 4 guages is you best bet, install once keep happy. you will need to run rcas from the head unit and a trigger wire. A fuse holder is the same weather it is 4 or 8 guage, so its just a matter of if you want to fork out for the bigger wire. In a 33 is is quite easy because you only have a matter of metres to get to the battery. A metre tops is probably all you will need. Remember you will need speaker wire to get back to you fronts as well. If you are doing it yourself, $50 - $60 as a pretty much top guide, depending on where you mount the amp. if you get it done pro, you could be looking at over $120 mark, if they wire speakers and all for you. This method usually leads to a longer life span due to less stress But if u have a little knowledge, this job will be quite easy.