Depends on what you call "normal trail shoes". I lot of what are marketed as trail shoes will be no good for your average XC; you usually will need something towards the fell shoe end of the market.
Most XCs in my part of the world tend to be largely on grass but there is the odd one with some tarmac so spikes are out for those. I personally use an Inov-8 x-talon which is fine for most XCs and will cope well with a small amount of tarmac. Also has the added benefit of being an ideal race shoe for most trail/multi-terrain races. The down side is that you could probably buy 2 pairs of spikes for the same price!
After many years of struggling with cold, wet feet in the winter, I have come to the conclusion that any sock with a significant wool content is the way to go. They may not be quick drying but do retain warmth when wet. I used to use Hilly trail socks but the quality has gone through the floor of late. Now using More Mile Vermont - 2 pairs for £10 @ startfitness
Depends what you call muddy really. Kanadias will be fine for some wet trails with a litttle mud but they do clog up quite quicky though this will depend largley on how wet and sticky the mud is. They are also quite cushioned - unecessary if its soft and wet underfoot. Taking it to the other extreme, I recentlly did the stourbridge stagger which was full on ankle deep wet sloppy stuff in places. Inov-8 mudclaws were ideal and Mrs S used x-talons and found they coped well too. Personally prefer a longer stud when the mud is really bad. There are plenty of other shoes out there which fit the bill. A longish stud but open tread pattern is what you are after so that they bite but then shed the mud.