Here is a suggestion port/subs to the front, here is a link to your sub specs:
http://www.skaraudio...cts/vvx-15.html
Assuming a final load of 1 ohm the 2500W RMS is high, set your subsonic filter to 25-27Hz.
Enclosure Specifications:
Fb = 30.011 Hz
Vb = 5 ft^3
External Height = 18 in
External Width = 48.5 in
External Depth = 18 in
Port Width = 4 1/4 in
Cut Sheet List:
* All Dimensions in Inches.
* Wood Thickness is 3/4 for all Parts.
External Enclosure Parts:
2x Front = 21 3/4 x 16 1/2
2x Front Internal = 20 1/4 x 16 1/2
Back = 48 1/2 x 16 1/2
Left & Right Sides: 16 1/2 x 16 1/2
Top & Bottom = 48 1/2 x 18
Shared Port Internal Assembly Parts:
2 x Front to Back = 14 3/8 x 16 1/2
2 x Extension = 13 15/16 x 16 1/2
Let me know any questions.