I need to replace some speakers in my subwoofers. I have 2 older Soundtech subs with 2-18" woofers in them. The original speakers foam has gotten old and broke apart. I believe the subs are ported, though I have not taken them apart yet. Emminence Sigma Pro's will work, but wanted to know if anyone here has another recommendation. The cab is tuned down to 28hz and the original configuartion is rated at 600 watts at 4ohms. Thanks for your help.