Hi chunk, I´m not too sure of the Agree or the Cervelo R5, but if I can give you my opinion, and this is coming from my experience with 2012 Cube Litening HPC Pro (Full campy SR) and an SWorks Tarmac SL3 (Full campy SR) then certainly the Sworks is more like a race machine - and this is pretty obvious. It is twitchier in the front end, and generally feels more lively, and of course has a solid and well proven winning pedigree. That said, the Cube is a solidly engineered bike. In my opinion they are well made, well spec´d and are reliable - I am certain that they will improve further now they have entered the Pro peleton with Wanty-Groupe Gobert (Litening is their race bike for 2015). They are light (with Campy SR around 6.8kgs with pedals), and comfortable.
The only major difference I can really relate to is the noticeable front end difference. The Cube seems higher set, and more solid. The Tarmac in this case is lively, and more agressive. If I had to choose between the two I would take the SWorks. Of course the price difference new would likely be vast between the two.
Something to watch - the Cube 58 is like a 56 in other brands. So be careful of this especially if you are doing a like for like and buying off the internet. Check the specs and the geometries in both bikes and try to come up with the correct sizing.
Once last point, and this is just me - I have really gone off internal cable routing lately. The Cube is a rattler, and I really hate that. I have elastic bands stuffed in everywhere to trying to stop rattles. Also consider that to replace cables or setup the bike it takes a bit longer and is more fiddly, and again this maybe just me, but I consider that my gear changes on exactly the same groupset are smoother on the external cable routed SL3.
To come back to your question though => do you spend the money on another bike or buy a power meter? Hmmmm, not sure. If you were to get the Cervelo, is it just the frame as you have written? Means do you have to take all components off the Cube and put onto the Cervelo, or it is fully spec´d? If fully spec´d will you sell your Cube, or keep as a 2nd bike? Reason I am asking is - if I was going to buy the Cervelo as a 2nd bike, then this would be my overall preference - 2 bikes, over 1 bike and 1 power meter. If it is only to upgrade the Frame, then I´m not sure it is worth the cost, and would go for the power meter. What components/groupset are you running? Which wheels do you have? Your investment is likely better in this area than changing the frame only.
Hope this helps
Hope this helps!
Facebook
Twitter
Instagram