I am planning to build a set of 3 way speakers early next year.

Rweeter, I plan on using Morel MDT33.
Midrange, I plan on using Morel MW142
Woofer, I am in two minds:

a) (2x) Peerless 8" (HDS series) 850490
or
b) (1x) Scan-Speak 21W8555 8".

I have two questions:

1. Which bass? The cost of 2x peerless is a little less than 1x SS.

Whilst the 2x peerless drivers will have a higher SPL, the SS has a much better low frequency rollof.
Plotting the SPL in WinISD gives the following results:

Peerless drivers have an F3 of about 60Hz with box size of 30 lit.
The SS has a F3 of about 29Hz with box size of 57 lit.

The peerless pair have a better group delay than the single SS.

The volume of 57l isn't a problem, because these will be floorstanding.
I do however want to keep to 8" drivers so the cabinets are relatively narrow.

2. I am going to have midrange and possibly woofer / tweeter attenuation problems. The SPL of drivers are below:

MDT33: 92.5dB
MW142: 86dB

450490: 91.2dB (I will however use this in the 90dB frequency range)
(2x) = 90dB + 3dB = 93dB

21W8555: 87dB.

With regards to the midrange attenuation problem: Am I correct in saying that baffle step will help me out here if I use the (2x) peerless drivers? The baffle step should push the midrange SPL up by a couple of dBs.

Alternatively I need to find a good midrange with higher efficiency.

Any advice would be greatly appreciated.

Regards,
Jim.