Good move on the face of it Sean.
First (and most important) consideration is strength.
Mechanical losses are generally lower through the lower ratio final drives
Gearing for an impossible to achieve theoretical top speed is a waste of time, unless you plan to use a lower (direct) gear in the box.
The lower you gear the car, the quicker it will achieve top speed, which will make for a quicker lap time, just so long as you don't under gear it to such an extent as to compromise top speed.

So, were these purchases your birthday presents to yourself?