Hi and welcome, post some pictures and model year (MY) to get the best advice.
Speakers - there are three systems, 180w, 380w Meridian and 770w Surround Sound. Depends on what you had before, what you are used too and quality you expect. If you search there are a few results this being one for reference - https://www.cartronics.co.uk/case-studi ... er-upgrade - but if your just doing front speakers then I guess anything will do.
Cold first starts - no need to wait, I don't if leaving early in the morning (although I prefer to wait for the revs to drop) and yes it does thump into gear more so in drive than reverse.
Tyres - should wear evenly. Glad you got it sorted.
My rears did 9k but my fronts are still on 4-5mm after nearly 16k now so expect them to last well into the mid 20k's. Quite a few suffer from inside front wear on the history checks I have done previously. As mine has perfect wear across the tyre and was perfect on Pirelli's 4-wheel alignment you might want to consider another alignment if you notice uneven wear on the new tyres
Enjoy. Pics please.