So, im getting this sometime soon (preordered).
However, looks like I might prefer a wireless connection from the router to my desktop to avoid unnecessary cabling around the walls.
What solution do I need to ensure that I can download/upload at full whack from my desktop without a drop in speed due to the wireless connection?
There aren't any. You are almost definitely never going to get gigabit speeds over wireless, unless you were next to an incredibly good AC router with a very good AC card. If you want the full gigabit speeds then cat5e/6a is the only way to go.
can anyone suggest an ssd that can keep up with a 1gbps download speed? will any ssd do?
Any SSD will be fine. In fact most harddrives nowadays will cope with 112.5MB/s which is what your gig speed is in megabytes