Mulching is great, but the lawn needs to be cut on a regular basis, and should be kept short - also the clippings when wet, will stick to everything...
17hp should be ok for such an area - again, with the mulching, it's just going to stop the clippings being routed to the grass box & thus give the grass another clipping. As these should be short clippings, should not be an issue for such horse power.
Other things that you should consider is the storage of the machine itself at night (added to your house insurance policy), regular servicing of the mower & costs. Transport of the machine etc...
Honda is a great brand - but expensive .. there are alternatives out there which are cheaper that do the same job - it's all in the looking after of your mower, regular cleaning, servicing.