Unless the piano is used professionally or institutionally for concerts,
recitals and such, a new set of hammers should last several decades.
Therefore, it is false economy to install anything but the best hammers
available, to get the tone you want.

Replacing grand piano hammers with "drop-in replacements" will, more
often than not, cause problems with the touch weight, backchecks, or
action geometry.  I recently saw a new set of Steinway hammers on a
1910 Steinway grand where the hammer tails had the wrong shape.  As
a result, the backcheck leathers, which held up fine for so many
decades, had been worn through in about a year.  The remedy for this
dilemma would be to replace the hammers with proper fitting ones and
to replace or releather the backchecks.

One interesting alternative to hanging a new set of hammers is to
have the old hammers refelted.  This saves a lot of labour and rules
out many of the problems that are often otherwise encountered.
Sometimes it is the only way to go because of the size and shape of
the hammer moldings (wooden core) for old or historical pianos or for
orchestrions.  Abel and Renner are among the top, if not the best,
hammer manufacturers.  They also refelt old hammers.  I have had
several sets of hammers refelted by Abel and the results are very good.

When thinking about new grand hammers, don't neglect the hammer
knuckles.  By the time the hammers are worn down, the knuckles are
usually flat and need replacing, too.  They play an important role in
the performance of the piano action.  Also, this is a good time to have
any repinning done.  All these work can be done by the refelters, if
preferred.

My great uncle had a saying: "We're too poor to buy cheap".  Having the
job done properly the first time will save you time, money, nerves, and
frustration and give you long term joy and satisfaction.  Go for the
best!

Jurgen Goering