I guess my recommendation for now would be... just ride the bike you have for now... You have 85 miles on your current bike, which is great - but it's not quite yet enough riding that you really know what your riding style is going to be and what you really want out of a bike yet. I know in the first year I was riding, I was switching things out and switching bikes a lot - and yes, definitely important to figure out what seat works for me, etc., but a lot of what was happening was just because I needed to develop my core muscles, and as I did... positions that were previously intolerable (mostly because of too much weight on my wrists), were suddenly fine and riding in a much more aggressive position was fine. I'm pretty sure what I ride now & love wouldn't have been quite what I picked if I'd put the money into it when I first started riding.

If you can find a cassette that works better for you for that, I'd definitely upgrade it...

After you have ridden more, have built up your core a bit - your riding style will evolve a bit more and then you'll be in a better position to really know what you want to buy... you don't want to buy another bike that you're going to outgrow quickly like the avail.

And as for what bikes you should be looking at.... test ride, test ride, test ride... and since you're looking to do it several months from now, that gives you time... Since you've mentioned you think you're cramped on your current bike... I don't think you should buy another version of that bike. You should probably consider fit more important than colors.

So SRAM vs shimano shifters - you're going to have to test them both out, sram's got the double tap system which lots of people seem to love. you mentioned you really like the short reach on your bike's shifters... and didn't like the shifter reach on the 105 bike you borrowed, so you probably need to be looking at something with the r700 or r600 short reach shifters, or realizing that you're going to have to shim or pay an extra few hundred to get the short reach shifters. Sram might have better reach.

aluminum can be harsh on bumps or long rides - so you might want to consider steel like Zen suggested or titanium or carbon. I haven't had any problems with any of the carbon components that I have. Steel can be heavier (definitely not always), and if you're trying to keep up with your bf, that might not be good. if you do go with aluminum, I'd say you definitely want carbon fiber seat stays and fork at least.