Fisherrose/Ben,
I'm not familiar with that model Systemdek- I'm more familiar with the suspended Systemdek derived from the Ariston, which in turn is incredibly close (almost exact) to the Linn tables. Those are excellent decks indeed.
This Systemdek along with the 900 and 920 model (and perhaps others) was also marketed under Dunlop- it's a non-suspended table, closely resembling a Rega in looks, and I suspect a nice table. The Rega 250 arm is a classic, and for very good reason. It's a very nice arm. The Ortofon OM3 is a budget cart and should be upgraded- although I own/run some nice moving coil carts like a Dynavector 17D3 and Ortofon Kontrapunkt B, I still love the Ortofon OM20 and 30 carts, and the new 2M carts like the Red, Blue, Bronze and Black are a perfect fit/match for that Rega arm. The Bronze gets a bit pricy though, and the red was not something that impressed me much. The blue would be a good option.
The Systemdek will require a bit more maintenance and skill to set up, but allows you to tweak and adjust the table, and allows more cart choices than the Technics. There's also less to go wrong, besides perhaps a belt dry rotting with time. No big deal.
The Technics SL-10 is a great table, perfect for a "set it, forget it, and don't ever sweat it" type of playback. The sound and performance is very good and the table, regarding setup, is about as hassle-free as they come. A better cartridge on it will yield great results- however you are limited more with this type of tonearm regarding cartridge availability.
My only real concern here is the table is more complicated, therefore more difficult to repair by nature, in the long run if anything develops an issue.
The model one down, the SL-7, is preferred by many an audio buff. I've heard one even further down, the SL-5 at an AK get-together with a Dennis Had class-A tube amp and Spendor speakers (owned by AKer Audiodon), and it was an extremely pleasurable listening session. It was clearly the best sounding room at the get-together.
I think the Audio Technica AT92E cartridge is the bottleneck with your current system.
The Project Carbon Debut- I like some of the ProJect offerings, but personally this table has left me underwhelmed on many levels.
The Systemdek has the potential to give better sound than the SL-10 with upgrades (especially that cartridge) and allows you to tweak/upgrade. "Potential" is the key word here.
As for dynamics, clarity, rhythm, less hiss/pop,- your cartridge, phono stage and record cleaning/condition will have more of an impact than the difference in the tables here. Hiss/pops may be record cleanliness or condition, clarity will be more affected by your cart choice, dynamics and rhythm, too.
If you stick with the Technics, a better cartridge will do wonders, but some of these linear trackers cannot take a different mat without affecting both optical sensors an also tracking angle. This table limits your tweaks/upgrade path.
I would say, if you want a minimal/no-hassle setup with minimal effort and easy to achieve good sound, keep the Technics and hunt for the best cart you can find for the Technics.
If you want a table you can grow with by tweaking and modifying and upgrading over the years, the Systemdek is your better choice here. That Rega arm is a great arm, but that cart needs to be upgraded pronto.
I'm a big fan of the Technics tables, but I would go with the Systemdek here- as long as you can afford tom upgrade that cartridge pronto.
