I’ve used this SVS SB-1000 with the Harbeth P3s with great results.
Adding to what yogiboy reports...
Am using a pair of SB1000s with Silverline Prelude Plus and Totem Forest speakers. Very pleased w/respect to the flexibility, bass-control, integration and cost of these subs. Yeah, I know, using them with "full range" floorstanders, not monitors and a pair, at that. SVS does offer an in-house 45 day trial with free shipping even on returns if you don’t like ’em. Sorry, can’t give you a comparison against some of the higher priced options you are considering.
The Harbeths are great, of course, and pretty stunning with a subwoofer. (done it). I have two suggestions. The first is to get a DSpeaker Antimode 8033 room eq unit, and the second is to go for two small subs rather than one large one. With your budget, I would go for the Antimode first, and then save for two SB1000 subs.
Thanks everyone. I'm still not sure if the REL T5i or SVS SB-1000 will be an improvement over my Energy S10.3. I guess I could always trial the SVS and send if back if it's not noticeably better. I've heard people note that upgrading their subwoofer made a giant difference in overall sound... even with something as affordable as the SVS. Any more advice is greatly appreciated.
REL pioneered the speaker level connection for better integration, but these days many other manufacturers have followed them.
From what I could find, the Energy S10.3 is not a particularly bad subwoofer at all. In my experience the sound quality of a subwoofer depends more on room integration than on the sub itself. I started with a very good sub (a B&W PV1d) and even that did not sound great until I added an Antimode 8033 for room equalization. The result was suddenly far tighter 'faster' and more 'tunefull' bass. My next upgrade will be a second PV1d to achieve smooth bass over a much wider listening area.. See here for multiple subs: http://www.acousticfrontiers.com/20101029using-multiple-subwoofers-to-improve-bass-the-welti-devanti...
willemj869 posts02-24-2018 2:09pmREL pioneered the speaker level connection for better integration, but these days many other manufacturers have followed them.Lets be clear and for quite some time. Many other manufactures provide high level connectivity to accommodate systems that lack a second set of low level RCA outputs for typical subwoofer connection. Some use the high level connection in conjunction with high pass filtering to filter the main speakers low frequencies. Non that I've experienced suggest this high level connectivity as a preferred method nor have I ever experienced high level connectivity used in professional audio applications.
Information suggests REL developed their own transformer design to aid in their proprietary high level connectivity. Regardless, every REL subwoofer I've connected to my system using their high level connectivity diminished my sound stage and added a level of noise. And in all cases their integration and performance was greatly improved by Velodyne Room Optimization and, I'm told, by other DSP methods.
The results of direct comparison are often ruthlessly revealing. In the end those results are a matter of subjective personal taste.
Robert OP, a DSP equipped subwoofer will last you many years and more importantly will easily adapt to most any room and or speaker you choose during your audio adventures. Tighter, less sloppy, slow, musical or home theater, are all red flag adjectives that describe subwoofers simply out of control. Add some DSP and many of those same units could sound quite good.
The 2 RELs I've used for years work beautifully and add zero noise to my systems (they've survived changes to everything else in the rig), and with them the soundstage is utterly enhanced and a sense of realism is added to the entire thing. If this isn't the case with anybody else's system it certainly isn't due to REL's well regarded designs. I'm not a DSP fan as I don't need it in my listening room, and I think DSP gizmos take a little of the soul out of systems by notching out a naturally occurring frequency, and add extra circuitry and tone decisions decided by whomever designed the thing. For "home theater" I use an old pair of good sounding box speakers and a simple receiver (2 channel…yeah man) so clearly I'm not part of that world. Other than that, DSP is great.