photonboy :
PCIe and PCI are the same if the model is otherwise the same. It just depends what you have spare on the motherboard.
If by not enough power you mean the volume is too low then that is likely an impedance (OHM) issue so you need to ensure the sound card is suitable.
The higher the OHM rating of the headphone the LOWER the volume will be. So if you had for example 600ohm headphones you need a sound solution rated to drive 600ohms.
If needs to be specific, I'm not exprienced in technical details of sound cards or headphones. My old motherboard was P7H55/usb3, It was sounding detailed and much more powerful than this one. I can say sound was crystal clear and detailed. Like, when you put on headphones and listen to music on high volume, they can hear you from another room. I just look for something just like it. P7H's sound card features: Via VT1708
High Definition Codec
Intel High Definition Audio Specification Rev.1.0 Compliant
Exceeds Microsoft Windows Logo Program (WLP) Requirements
High-performance ADCs with 90dB SNR, DACs with 100dB SNR Various Output Format
4 Stereo DACs Output Pairs supporting 16/20/24-bit, 48/96/192/44.1/88.2 kHz sample rate
2 Stereo ADCs supporting 16/20/24-bit, 44.1K/48K/96K/192KHz sample rate
2 independent 16/20/24-bit S/PDIF TX Outputs supporting 48K/96K/44.1K/88.2 KHz sample rate
Others
HPF In ADC Path for DC Removal
High performance analog mixer for AA path
Two Jack Detection Pins
Power Supply
Digital: 3.3V
Analog: 5V
Built-in 5V to 4.4V LDO (Low-Dropout) Voltage Regulator
Supports External Amplifier Power Down (EPAD)
Power Management and Enhanced Power Saving Features
http://www.via.com.tw/en/products/audio/codecs/vt1708s/