Sovtek's 12AX7LPS is the best choice for HiFi Audio with excellent sonics. It has a long ribbed plate derived from Siemens design, with a filament that works with both AC and DC supply. 12AX7LPS has great low-mids that provides warmth without the mud. If you are looking for the right tube warmth at a great price point, Sovtek 12AX7LPS is your best bet.
Please note that the filaments in 12AX7LPS tend not to be very visible, even when it is fully lit. This is by design and perfectly normal. On 12AX7LPS, the filament is spiraled to reduce hum noise, and in addition, the ends are not exposed to further reduce the noise.