Legacy Product accounting for low speeds?

[#1]

I've experienced extended periods of slow speeds for quite a while and have noted the newsgroup announcements so have waited patiently but raw statistics don't match perceived performance and I wonder if it's related to my product or part of a continuing general problem.
Broadband Plus upto 8Mb (and within monthly allowance).
PC wired to Netgear DG834G (v2) plugged into BT main socket and connected to pte-ag1 with download speed/attn/noise = 7328kbps/25db/9db and upload = 448/6.5/25
Exchange is reported problem-free and speedtester.bt reports (profile = 6000: also per PN)) 5574Kbps.
thinkbroadband reports are not consistent. The page takes an age to load but the test itself (eventually) reports figures such as 2.9/0.4Mbps and 5.2/0.4Mbps.
mybroadbandspeed reports speeds as 200/59kbps, 252/91kbps and 189/68kbps (latter= 23.6/8.5kB/s).
All figures are from this afternoon but the perceived speed is the same during weekdays and I suspect that tests over the next few days won't mean much anyway so am posting now. All clues gratefully received.

[#2]

Whilst you have no doubt read that PN have been having some network issues, this will have contributed to some of the slow down you may have observed, quite a few of the problems are getting ironed out and there have been improvements in the last couple of days, but it certainly isn't your product causing the issues.
Speed throughput testers can give different results from one moment to the next at peak times due the variability of traffic at the exchange as well as the ISP's network. You should notice little variability at of-peak times and results should be very close to your profile. You've obviously checked you BT & PN profiles are correct.
What I do note is that from the stats that you have given, with that DS attenuation you should be syncing at max. speed.
Do you leave your modem/router on 24/7? and at what time and how long ago did you last sync? if it was last switched on at a very noisy time, eg. mid-late evening, then this may account for it. You do seem to be picking up a bit of noise that may be causing a lot of errors and this will slow down throughput as well as causing a lower sync speed.
Can you her any crackling or other intermittent noises on your phone line?

[#3]

Thanks for your helpful response.
I very rarely turn off the modem/router but last bounced it on Monday at 17.30 (to see if that solved a problem which turned out to be a duff switch) and hadn't appreciated that timing made a difference. I'll bounce it again in an hour or so.
The BT quiet line test sounds... quiet.
I've just repeated the mybroadbandspeed test and the figures have jumped from 189/68 eight hours ago to 5397/346 kbps!!! Quite some variation.
Figures from earlier in the week had already been discarded as I hadn't noticed until early today that Opera had dropped into Turbo mode when auto-detecting a slow connection so, given that I don't know when it did that, those figures probably wouldn't be a valid basis for comparison.

[#4]

I would advise that you try for a re-sync between 9am and 3pm when noise levels are generally at their lowest. If you have a lot of local noise, resyncing at other times will be detrimental to your performance. I don't thinbk ther's much point in looking at throughput speed resulkts for a while until we've sorted out your sync and profile speeds. Can you post the latest full ADSL line stats including the power figures?
Can I also suggest that you do a resync by powering down for 10 minutes (rather than a reboot) - we don''t want DLM thinking you have a dropping connection.