I have researched for like 8 months strait sitting, listening, driving, sampling... Im gonna have a small system guys, (2) 6" Midrange in each door, (2) Selenium $20.00 super tweeters per door, On a Sundown 175.4 at 2 ohms per channel. With a nice EQ, It should be enough for me and my friends witch is what Im going for. I want to be LOUD in the vocals, and SMOOTH AND PRESENTABLE WITH THE BASS OUTPUT. I may add (2) More 10's or maybe switch to 15's AND YES I will Have 8" mid-bass in the doors, maybe 10" AND yes it will sound Clean AND loud. When I say SQ I mean LOUD SQ. VERy NICE SOLID, RE-In-forced sound. What I need help with is the calculation for a dual 10's T-line specific to SA-10's , Over-kill.... I dont think so... There more like not super tweeters, and (1) Mid in each door, even seleniums, Dont get loud enough for me when I'm trying to get in the mood. SUMMER....SPL....SQ...T LINE...SUNDOWN...CRESCENDO... i know 2150w rms is more than enough for a t line design, I know Its louder than some like it, Who cares? lol, Im here with a question about T-lines, not what I LIKE in MY car!!!!