Hi Rebecca
How exciting for you picking paint colours ... and how daunting too.
IMHO it is the light in the room rather than the paint that has the most influence ... eg. in a small dark room, no amount of white paint is really going to brighten it up.
The paint finish is purely a personal choice ... I don't think having soft sheen rather than matt paint will make a whole lot of difference really. Assuming you don't have sticky fingered children running around ...! Have you considered using natural paints ... ?
I would suggest a consulatation with an interior designer would be money well spent at this stage ... a new house can be overwhelming and mistakes can be expensive. Plus I think you have to be living in a house to get the feel of it to know what really works and doesn't work, where an interior designer has a trained eye for this kind of thing.
If it's any help, I will give you the details of the lady I used in Athlone by PM ...
HP