I have no idea what I am looking for in a road bike.
DO I want a cyclo cross or a road bike for commuting? At 6'4" with long legs what sort of frame size am I looking at? Where does my money get well spent price wise? Is there threshold point where there is a big difference in kit?
A factor might be what the commute involves.
Is it urban only?
Are you likely to be able to use other paths than roads? If so, CX. Otherwise, road but you should really try both out and ask yourself what you want?
Road - look for a brand that's putting more into the frame, as you would with MTB. If you're comparing a "carbon" bike with 105 with a carbon bike with 105, you are generally not comparing like with like. See if you can demo some? What's your price limit? Spec-wise, all works fine - Tiagra's great but I would use either 105 or SRAM Rival. No sense in spending more than those groupsets to me.
Do you want a comfortable bike or a more racey machine? Perhaps a touring bike would make more sense if you're only using it as a commuting bike or maybe even a light tourer such as a Surly Cross Check.
Sorry, asking more questions than I'm answering.
If your after a road commuter buy an "audax"/"winter trainer" type bike, if only to be able to fit mudguards.
Other than that make sure you have some form of STI/Ergo/Double tap, the different shapes suit different people, and there is always the issue of the tools you need.
As for size, not sure i am 6' and ride a 57cm so i would suggest starting at 60cm and going up from there. But go to a shop and get properly sized.
£1k will buy you a good road bike these days, if it was just for commuting i'd go for a cx bike.
If commuting in winter too, buy a hack bike, cus the weather will kill it dead.
I am selling a road bike. Not sure if it is suitable for your needs but it should be the right size.
Details here: http://www.singletrackworld.com/forum/topic/specialized-roubaix-comp-road-bike
It's downside is that it doesn't have fittings / clearance for mudguards which might be important on a commuter. But it is a very nice bike:)