What tube amp for starting out?

Marco, I can do a number of accents as required. I do a particularly good Eastern Indian, but I'm afraid the present PC culture will not allow it.

At the very least, it should double it's wattage into 4 ohms from its 8 ohm rating, otherwise you will hear a recess in these regions. Frankly, this might explain what you're presently hearing with the Dynaco amp when you say the sound is "dead in the midrange".

could the 4ohm output taps be used then?

4 ohm taps would be a requisite with the Infinity loudspeakers, but this
is not a guarantee that the Dynaco doubles power into 4 ohms. The
Dynaco can probably be adjusted so the taps are 4 ohms, if they don't
already allow for this.

Another option would be trying Speltz Zeroformers that double, triple or
quadruple impedance...effectively doubling the Infinity's 4 ohm
impedance to 8 ohms, but they also would double the 8 ohm impedance
to 16 ohms, so the curve wouldn't change even though the load would
become easier. I've never tried them myself, so I have no idea how they'd
work, but theroetically they are an option for this scenario.

The advantage of an amp that doubles its wattage into 4 ohms versus 8
ohms is that it flattens out the speaker's response curve. Therefore
certain frequencies aren't emphasized over others, as would be the case
with the Inifinity's dip in the lower midrange and upper treble
frequencies.

Personally, I'd rather have a good speaker/amplifier match without
having to add fixes in between.