So, I have an Allez Elite (E5 alu, FACT carbon forks, Tiagra groupset, and I just gave it pretty much the ultimate test an amateur can give a bike. I rode it unmodified (apart from Look Keos, Fulcrum 5 wheels and a Prologo saddle) 1199km from Paris to Nice with the Polocini crowd. This included several categorised climb, including Mont Ventoux (yes, on a 34-25!!!). 15,000m of climbing. 8 days.
How did it do? Well, it could do with a 27 or a 30 on the back for HC climbs. The front mech got twisted by cross-chaining under load. The headset came a little loose. It started over shifting on the front and dropping the chain. Extra padding is needed on the bars because I ended up with ulnar palsy. It blew up a Gatorskin on a descending curve.
Essentially, it was COMPLETELY FINE. The mech thing was my own fault for cross chaining, and the tyre was unavoidable. My 2011 model needs a bigger rear sprocket (Fred Salmon is fitting one and this involves a mech swap for 105). Fred's comment was that Tiagra would be expected to wear out a bit on a trip like that.
The bike is 9.5kg, and was probably the heaviest on the trip (others had Van Nicholas Ti, A Ti September, a Trek Domaine, a Trek Madone, a carbon Dolan and an insanely light Moda Stretto). But once you add a bottle and a rider, the 2 or so kg differences mean nothing. The geometry, although borrowed from the Tarmac, is fine for eight 100-mile days back to back, and I put up 2h 4mins on Ventoux (it was windy, OK? ;-))
My conclusion from this is that if the bike fits and is reasonably modern, then you can ride anywhere on anything. I have got a bike in my head though, and it's for reasons of desire rather than need (Wilier GT with Campag EPS), and it would weigh nearly as much as the Allez and have the same gearing.
Enjoy the Allez, and don't over agonise on the new bike. Just get something you can afford and fall in love with ... and that fits. All else is flim-flam.