PH wrote:Other than the tyres I don't see you've much to gain from any cheap upgrades.
If it hasn't already had one, give it a good Spring strip down and service, if it's had much winter use I'd replace the cables, maybe for some upgraded ones, I like jagwire. When I know a bike is spot on with everything exactly as it should be it always feels like an upgrade even if it has no new parts.
That's what I reckon too. As comfort is part of your aim, how about re-examining your 'fit' and contact points and consider any changes to that - are you happy with your saddle or do you think you could do better? Likewise handlebars and tape (I'm presuming you ride drops). I've recently been through a Goldilocks phase with my handlebars. I wasn't completely happy with the short reach compact bars that came with the bike - the only hand positions off the drops were on the hoods and on the tops (and not much difference in reach between the two). I tried the Modolo Gran Fondo bars which to me were lovely except for the drops which I hated and I ended up with a shorter stem and Velo Orange Grand Cru Course (with a much longer reach than my original bars) - but I do like to move about on the bars quite a lot compared to some. With the new bars, it feels like a different (and better) bike.