http://www.infinitysystems.com/homeaudio/product_detail.aspx?prod=TSS-CENTER4000PLT
Center Channel
Frequency Range: 120Hz – 20,000Hz (+/–3dB)
Recommended Power Amplifier Range: 10 – 150 watts
Sensitivity (2.83V @ 1m): 89dB
Nominal Impedance: 8 ohms
Crossover Frequency: 1,000Hz, 3,800Hz; 24dB/octave
Low-Frequency Driver: Four 3-1/2" MMD™, magnetically shielded
Midrange Driver: Dual 3-1/2" MMD™, magnetically shielded
High-Frequency Driver: 3/4" MMD™, magnetically shielded
Dimensions
(H x W x D): 4-1/8" x 23" x 4-3/8"
(105mm x 584mm x 111mm)
Weight: 12.7 lb (5.8kg)
this is just 15mm (5/8") over your 3.5" requirement