Boiler quotes

rev_henry

I have thus far had 3 quotes from reputable companies to replace our old boiler which I fear is on its last legs. Its a combi around 25 years old, running a bath is getting more and more difficult and I don't think there's any point spending any money on it.

1. Vaillant Ecotec plus 825. 8 year warranty £2100 OR ecotec pro824 6 year warranty £1900. PLUS magnetic filter £130. PLUS optional powerflush £300.
2. Glow worm ultimate 30, 10 year warranty £1800
3.Vaillant ecofit 825, 7 year warranty, £1650. Although that will probably be nearer £1700 as that quote only included a basic timer which we've since decided we want a better wireless one.

1 seems expensive, 2 and 3 include the magnetic filter which I understand one would be foolish not to have these days.
I am inclined to go for 2 at the moment for the 10 year warranty.
The added complication is that apparently we only have a 15mm pipe to the boiler which may or may not need upgrading to 22 or 28mm. All 3 seem to think we will probably be ok without. 1 and 3 have recommended we go no higher than 24/25kw for this reason, which begs the question why has 2 quoted for a 30kw. Only 3 has quoted for upgrading the pipework for an additional £250.

Does anyone have any thoughts on the above. Are we likely to need the pipes upgrading? Should we not go for the 30kw for that reason? Do we need a powerflush? Will the 24kw be ok for running a bath? And are any of the above boilers better than one another?