Re-boring requires pistons to fit.
Since Honda pistons and rings are far from cheap, the 836 kit is not a huge added expense over what you would need to pay.
However... yes, reboring is the way to go to restore performance to a worn engine. Is yours actually worn to where it needs a rebore? Once you have the engine apart have the cylinders measured by a good shop. If they're within wear spec and round (cylinders worn oval don't seat new rings very well) then get a new set of rings, set the end gap properly, run a cylinder hone through the bores to roughen up the surface for ring seating. If the pistons are worn out you're looking at a big price tag anyhow so again the 836 kit may be the best option. Check the valve guides for wear and replace if neede, try just lapping the valves if not: a nice even polished ring around each valve and seat says all should be well. For a valve job should new guides be needed cut as little as possible from the seats and avoid grinding the valves - they are stellite coated, a very thin hardened surface meaning grinding them gets into the softer steel which will not last as long as new valves with an intact stellite coating.
Once you do an 836 kit the cylinder sleeves are done; you don't have an overbore available if you manage to wear out the bores again. With the usual mileage our bikes get though, this shouldn't be a problem. Replacement sleeves are available for that far off day anyway and hopefully will still be made then.
