Transformers for CNC power supply and connections

Well I type a big long post and it looks like yahoo eat it so here it
is again.

I need to make a power supply I would like an out put of50Vdc - 80 Vdc
and 8-15 amps.
Someone on this list e-mailed me and said to wire 2 of these in
series:
http://www.mpja.com/product.asp?product=7846+TR
24Vac 10 amps. in series that would be 48Vac * 1.414 =67.8 Vdc.
A EE student I work with told me I could not wire transformers in
series. (but I don't think he is correct or very bright)
Can I wire the outputs of transformers in series to double the
voltage? Can I run them in Parallel to double their amprage?
If so I should be able to buy 4 of these 25V / 7.5 amp transformers.
http://www.sciplus.com/singleItem.cfm?terms=2294&cartLogFrom=Search
Build 2 sets that are in series, so I would have 2 50Vac 7.5amp
transformers then wire the 2 sets in Parallel to get 50Vac 15 amps.
when I rectify that (50Vac * 1.414= 70.7 Vdc @15 amps)
Is this correct /acceptable?
I guess it would look like this"

25V/ac7.5A TF => 25Vac/7.5A TF \
\
50Vac/15amp =>rectofier => 70Vdc@15A
/
25V/ac7.5A TF => 25Vac/7.5A TF /

Jerry