I'm looking at a bike on Ebay right now. Might be serious about it if the price ends up being right.

I need some geometry advice, and some general advice about buying a bike without riding it first.

I'm 5'6". Currently riding a 54cm Felt F50 (it's a 2004 model, don't think they make this one anymore). TT 54.5 cm, currently running a 90mm, 0 deg rise stem (parallel to the ground). HT angle is 73 deg, ST angle is 74.5 deg. Headtube is 11 cm.

I got a great deal and I've learned a lot on this bike, but it's really a little too big for me. With the current setup I get lower back twinges at 40 miles or so.

The bike I'm looking at has a 52.5 cm tt, and is half a degree slacker in both angle measurements. HT is 12 cm.

A few questions:
1. Is 2 cm (plus a 1 cm higher ht) going to make a big difference in reach, enough to soothe my lower back? Too much???

2. Will half a degree difference in seat tube/head tube angle make a big difference in either
a) handling
or
b) balance/pedaling efficiency (I tend to prefer a more forward position -- though maybe this is in part because my bike is too big?).

3. Is it a really bad idea to buy a bike that is intended to become one's "primary" bike over the internet, without the benefit of a test ride? Having helped my boyfriend test bikes last year (and having ridden probably a dozen bikes in the process) I do realise that even high end bikes have very significant differences in handling and road feel.

OK, since it's obvious anyway , I AM talking about the Litespeed advertised on TE yesterday.

And, I know this is a lot of stressing when there's not a shred of guarantee that I'll even win the auction. But thanks for any advice anyway .