5 Channel Alpine MRP-F320, 30 watts x 4 + 120 watts X 1 @ $280 MSRP
I'm not the best on cheap but good subs.
What I like is JL WO but it may not be the $87 that the W1 was. I would not get the W3 or W6 or W7 stuff.
Better subs for a little more $$ would be Image Dynamics IDQv2. A 12" IDQv2 will run on 120 watts and love a 0.7 cf box.
Have no experience with Lamda but many say it's great sound but not expensive sub.
Regardless of who's sub you get, I would get one 12".
There are some good 10's but a 10 or 8 will need more excusion to produce lower frequencies when compared to a 12 or 15. You can get clean low frequency response with low power out of a properly designed larger sub. You don't want a 15 because you may need the sub to run high, like 120 Hz (crossover at 80hz), to meet your door speakers.
You don't want to buy power hungry SPL monsters like W7, Kickers and the like and run them off 120 watts. They will never work with the 120 watts.
With the W0 and 5 ch amp you will be able to 120 to 130 dB.
Anthony B. Davis
2Deep2 Silver SVT
2002 IASCA SQ Ult Ama 601+ World Champion runner up
2002 SLAP dBQ Champion

2000 USAC SQ World Champion
2002 USACi SQ World Champion