A new 1M / M2 would destroy the A45.
The A45 is going to find it hard enough to beat the M135i for everything except looks.
I hope the A45 is a good car, but the following things don't stack up for me:
2.0 engine
Haldex 4WD
List price
No LSD (in 1M not M135i)
The N55 BMW engine is sensational.
That said I will give it a go when it arrives, but think its direct competition will be the S3 Sportback and obviously the M135i.
The RS3 and new M2 will be a league above.