You don't say how you're judging the quality of Premiere Elements' video -- whether you're just playing the timeline or you've output and, if the latter, what output settings you're using and what media player you're using to view it.
But the biggest challenge is that version 8 of Premiere Elements does not interface well with AVCHD. That didn't happen until version 10 (and then got even better in version 11).
But that said, this workflow will give you the best possible results:
1) Make sure your camcorder is set to record 1920x1080 AVCHD.
2) Start a new Premiere Elements project and ensure that you've selected the settings for Full AVCHD 1920x1080. (You can't change your project settings mid-project, so you need to do this when you first start your project.)
3) Connect your camcorder via USB and use Premiere Elements' Get Media/From AVCHD or Other Hard Drive Camcorder to get the video from your camcorder to your computer.
4) Once you've finished editing your video, output your video using Share/Personal Computer/Windows Media using the HD 1080 30 preset. Play your output video on the excellent, free VLC Media Player.
As I've said, the biggest problem is that version 8 was built back before anyone knew how to edit AVCHD video. There's not an AVCHD Share output setting! But this is will give you the best possible throughput from version 8.
My advice? Upgrade to, at the very least, version 11. Current versions of the program work much more effectively with AVCHD -- and, in fact, even set up the project settings automatically, based on the footage you feed into it.
Otherwise, you'll be living compromised video. Premiere Elements 8 is unfortunately ancient history, video-wise.
In replying to your other thread just now
I have included comments about you using Premiere Elements 8.0/8.0.1 to edit your AVCHD video.
I believe that Premiere Elements 8.0/8.0.1 can be used successfully for your current video project provided we factor in the way the program is setup and
certain computer resources issues associated with the high resource demands of editing the AVCHD format. And, if you are going to export your Timeline content to a file saved to the computer hard drive, I would go with Share/Personal Computer/MPEG instead of Share/Personal Computer/Windows Media in spite of the smaller file size that you would expect to get from the Windows Media choice.
If computer resources proves an issue, many using 8.0/8.0.1 convert the AVCHD to MPEG2.mpg (a less resource demanding format) before the file is imported into Premiere Elements 8.0/8.0.1. Burn to disc in 8.0/8.0.1 needs more considerations when it comes to larger projects and burn to Blu-ray disc format on Blu-ray disc.