special design, especially in low-mid price amps, tends to mean "specially designed to be as cheap as possible, quality of tone be damned!"
i have a special design celestion in my marshall avt100. i mean, seriously, i could probably design a better sounding speaker, and I only have gcse physics, and I got it about 7 years ago...
so yeah, don't judge eminence by your "special design" speaker...