if the receiver has a true PHONO IN connection, then it will handle the RIAA equalization and a phono pre-amp is not required.
The phono pre-amp is usually required on newer receivers that do not have a phono input and the turntable would have to be connected to an auxillary audio input. The turntable output from the cartridge is usually too low for a typical line level audio input, and the non-phono input will not have the equalization circuitry to reverse the RIAA compression used when the record is pressed.
http://en.wikipedia.org/wiki/RIAA_equalization
the HK 3390 is a very nice stereo receiver. It has the phono input and a subwoofer pre-out to drive a powered subwoofer in a 2.1 setup. You would use a simple RCA audio cable for a short run to the sub, or a digital audio coaxial cable for a longer run
http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10236&cs_id=1023601&p_id=6304&seq=1&format=2
"trigger" is a switched voltage to turn the powered subwoofer on or off with the receiver. Most new powered subwoofers have a sensory circuit to turn the amplifier on when it senses voltage on the input from the receiver and the trigger is not needed.
for "normal" runs of 3 to 6 feet, the plain jane RCA red/white audio cables will work fine for your interconnects. You can get "premium" cables at an excellent price at Monoprice for just about any length
http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10218&cs_id=1021803&p_id=2864&seq=1&format=2
a suggestion...budget to replace the Polk PSW10 subwoofer - it does not have the best reputation as a "musical" sub - it was made for a price point and there are better units available as you upgrade your system.
There is a long standing opinion variance on "towers vs. bookshelf with subwoofer" speakers. Towers to have an extended range of audio reproduction, but higher quality bookshelf units can match that as well....it is all a matter of dollars spent. Whatever you use, I would still have a good powered subwoofer in the system to take the heavy lifting of reproducing the lower frequencies (often present in classical music with it's wide dynamic range) and free up the receiver to handle the mid and high frequencies.
At a modest budget price point, there are the Polk Monitor 70 towers
http://www.amazon.com/Polk-Audio-Monitor-Floorstanding-Speaker/dp/B0002Z241Q (
www.newegg.com is out of them at the moment) and the Infinity Primus P362 towers
http://www.crutchfield.com/p_108P362BG/Infinity-Primus-P362.html?search=infinity+primus
For serious music listening, you might want to consider a CD player, or DVD player that can handle SACD or DVD-A high quality lossless digital recordings.
It is a wonderful hobby, and classical music demands a lot from your equipment. Beware "upgrade-itus", you wallet can get seriously overheated as you budget and spend more and more on "better" audio equipment
welcome to the world of great audio...and guard you wallet !!!
PS: speaking of your wallet, just stumbled on this sale price on a new HK 3390
http://www.vanns.com/shop/servlet/item/features/540349400/harman-kardon-hk3390?s_c=site_search I have ordered audio equipment from Vann's before and was very satisfied with their service.