That woofer has only an 18 cm diameter which explains a power handling of 70 watts.
Among the best subs for a DIY project are as stated in my previous post, the Dayton brand of drivers are excellent products. If you prefer an 18 incher, the RSS450HO-4 is an excellent subwoofer and believe TLS Guy has been recommending them to audiophiles. However, if you intend to use the sub for serious music listening, I would think that the 15" RSS390HF-4A would perform more accurately, but I may be wrong.
What I would suggest are 2 RSS390HF-4 for accurate music reproduction, or the RSS390HO-4 drivers if their main purpose would be to listen to movie soundtracks.
Since I am only familiar with the RSS390HF-4A but have had no experience with the HO version in either the 15 inch and the 18 inch units, I believe
@TLS Guy will be able to clarify the situation based on his experience and knowledge.
We should have an answer on this question in a short delay.
With regard to an amplifier to drive the sub(s), a Crown XLS series amp should do a satisfactory job. Several members have been using them with satisfaction. Depending on whether you will be driving one or two subs, the amp power could be chosen.