mono block or bi-amps which would you pick?

Zipost, it sounds like the biamp alternative you are asking about is what is referred to as a horizontal passive biamp configuration, meaning one stereo amplifier for the mid/hi sections of the speakers and another for the bass sections, without using an electronic crossover "ahead" of the amps.  While some audiophiles use such a configuration successfully, it has many potential pitfalls that can lead to unsatisfactory results, especially if the two stereo amplifiers are different models.  And if the two amps are identical models, a better way to biamp them would be in a vertical passive biamp configuration, meaning that each amp would power a single speaker, with one channel of the amp serving the mid/hi section of the speaker, and the other channel serving the bass section.

In contrast to a horizontal biamp configuration, a vertical configuration would allow you to use shorter speaker cables, as in the case of the monoblock alternative.  And perhaps more significantly, it would also mean that both channels of each amp are processing the same signal, which can potentially reduce inter-channel crosstalk effects within the amp.

That said, with a biamp approach you are of course paying for four channels of amplification, while if you purchase a pair of monoblocks you are paying for two channels of amplification.  So assuming comparable power ratings for the two alternatives (and keep in mind that the difference between 250 watts and 100 watts is only 4 db) it would seem that whatever amount of money you decide to spend on amplification stands a good chance of getting you better quality amplification in the case of the monoblock approach.

Good luck.  Regards,
-- Al
  

Assuming the speaker specs are accurate, which can often be a big "if," and assuming about 3 db of "room gain," it can be calculated that 28 watts into each of the two speakers will produce an SPL of about 106 db for a centered listener sitting 10 feet from the speakers. 60 watts would produce about 3 db more than that.

Either number is more than enough volume for most listeners on most recordings. Exceptions are likeliest to occur on material having extremely wide dynamic range (i.e., a particularly wide difference in volume between the highest volume and lowest volume notes on the recording, such as some large scale classical symphonic recordings that have been well engineered with minimal or no dynamic compression), or if you routinely listen at the levels that are often encountered at live rock concerts.

Regards,
-- Al